Hoff was far too scholarly and intelligent a man to commit the blunder of 'confusing' the caduceus with the serpent staff of Aesculapius. The sign of Mercury was deliberately adopted, as I have heard him state, because it was the emblem of the merchant and hence the emblem of the noncombatant. In junctures when it was necessary for a vessel to proclaim its nature, it was customary for a merchant vessel to indicate its noncombatant status by flying a flag which bore the emblem of Mercury, the God of the Merchant. The caduceus, in our use of it, is not distinctively the emblem of the physician, but the emblem of the whole Medical Department. The enlisted men of the medical department outnumber the physicians of that department. Besides the ambulance wagons, many vehicles are employed in field service in war which are not distinctively medical, but which are used for medical purposes. Both the enlisted men and the vehicles of the department (not to mention many other objects), should bear some sign of neutralization for protection. It seemed to Colonel Hoff and to the board that the Geneva cross, which in addition to its use as an emblem of neutrality is also the emblem of the Swiss Republic, there might well be substituted an emblem which is not the emblem of a foreign country, and the caduceus was selected, as the emblem which for many ages has served to indicate the noncombatant.

— William K Emerson, Encyclopedia of United States Army Insignia and Uniforms[25]

According to this view the caduceus was not intended to be a medical symbol (and, though explained differently, this reflects the view advanced by the editor commenting in The Army and Navy Register of 28 June 1902 discussed above). Nevertheless, after World War I the caduceus was employed as an emblem by both the Army Medical Department and the Navy Hospital Corps.[citation needed] Even the American Medical Association used the symbol for a time, but in 1912, after considerable discussion, the caduceus was abandoned by the AMA and the rod of Asclepius was adopted instead.[5]

The Army Medical Department (AMEDD) has included the Rod of Asclepius in its regimental coat of arms since its foundation in 1863. (Although now part of the AMEDD, the Army Medical Corps retains the caduceus for its own plaque and insignia.) The medical insignia of U.S. Air Force uses the rod of Asclepius.

Despite widespread acceptance of the caduceus as a medical symbol in the United States, it has been said that the rod of Asclepius has "the more ancient and authentic claim to be the emblem of medicine".[26] Most attempts to defend the caduceus's use in a medical context date from the last quarter of the 19th century through the first quarter of the 20th, and have been characterized as "based on flimsy and pseudo-historical research".[10]

In a survey of 242 logos used by organizations related to health or medicine, Friedlander found that professional associations were more likely to display the rod of Asclepius (62%), while organizations with a commercial focus were more likely to use the caduceus (76%). Hospitals were an exception (37% used a staff of Asclepius whereas 63% used a caduceus). Friedlander felt it likely that this might reflect the fact that "professional medical organizations have more often sought a real understanding of the meaning of the two symbols whereas commercial organizations have been less interested in the historical basis of their logo or insignia and more concerned with how well a certain symbol will be recognized by the iconographically unsophisticated audience they are trying to attract to their wares."[3]

The use of the caduceus in a medical context has long been frowned upon by many professionals, academics and others who are familiar with the historical significance of both symbols. This has occasioned impassioned remarks by those frustrated with the continuing confusion.

It is hard to trust a profession that cannot even get its symbols straight. Most physicians in the United States think that the symbol of their profession is something called the caduceus. But this is actually not true. [...] Historians have discovered that someone in the U.S. Army Medical Corps mistook the caduceus for the Aesculapion and introduced the Medical Corps' symbol at the beginning of the twentieth century. Soon thereafter, everyone in the United States was emulating the mistake.

— Daniel P. Sulmasy, A Balm for Gilead: Meditations On Spirituality and the Healing Arts[27]

It has been said that the caduceus is particularly inappropriate for use as a medical symbol due to its long associations with the Greek god Hermes, who was patron of commerce and traders as well as thieves, liars, and gamblers.[28]

As god of the high-road and the market-place Hermes was perhaps above all else the patron of commerce and the fat purse: as a corollary, he was the special protector of the traveling salesman. As spokesman for the gods, he not only brought peace on earth (occasionally even the peace of death), but his silver-tongued eloquence could always make the worse appear the better cause. From this latter point of view, would not his symbol be suitable for certain Congressmen, all medical quacks, book agents and purveyors of vacuum cleaners, rather than for the straight-thinking, straight-speaking therapeutist? As conductor of the dead to their subterranean abode, his emblem would seem more appropriate on a hearse than on a physician's car.

— Stuart L. Tyson, "The Caduceus", in The Scientific Monthly[4]

On the other hand, it has also been remarked – not without considerable irony – that commercial aims in medicine, especially in the United States of America, make the caduceus an appropriate symbol, at least for some physicians.

Well, so much for the caduceus. Somebody obviously got the wrong symbol for modern medicine–or did they? The caduceus seems to be an appropriate symbol for modern commercial medicine. Of particular relevance are the functions of escorting souls of the dead, wisdom, fertility, commerce, luck, eloquence, cheating and thieving. These have become symbolic of how medicine evolved in the late Twentieth Century.

— Luke Van Orden, Where Have All the Healers Gone?: A Doctor's Recovery Journey[29] The Caduceus and the Rod of Asclepius as used by neighboring offices (Ridgewood, NY)

Others are unapologetic about the association of medicine with commerce, recognizing the importance of "advertising essential for competitive marketing", and suggesting that it is up to individual physicians to choose between the two symbols, based on their own views about what associations are appropriate.[30] The AMA has used the Rod of Asclepius for over a century,[31] and its current logo since 2005.[32]

In North America, there are calls to clarify the symbol and to move to a uniform use of the rod of Asclepius. For example, the director of communications of the Minnesota Medical Association is quoted as saying, "If it's got wings on it, it's not really the symbol of medicine; some may find it hard to believe, but it's true. It's something like using the logo for the National Rifle Association when referring to the Audubon Society".[33]

However, Andrew Weil, a proponent of alternative medicine, has suggested that the caduceus is appropriate as a medical symbol "because it embodies an esoteric truth that must be grasped to gain practical control over the shifting forces that determine health and illness."[34]