In these days of alarms and excursions, wars and rumors of wars, many in civil life must be giving thought to the possibility of serving in the Army or Navy in their professional capacity. Those who contemplate such a move must be wondering just what military or naval service would mean to them. I shall try to describe some of the work of the naval medical officer under various conditions at sea or ashore. Many doctors have entered the Naval Reserve and are now serving on active duty. It has been my privilege to serve with a number of them and I am glad to pay tribute to the willing, cheerful manner in which they have so efficiently aided the rapid expansion of the Naval Medical Department. They have in some cases sustained a violent dislocation from their accustomed daily life into a strange environment. They have almost without exception accepted the situation gracefully and adapted themselves quickly to the new conditions. When the medical man wishes to enter the Naval Reserve, he makes application to the Bureau of Medicine and Surgery at the Navy Department in Washington. If he is professionally and physically qualified he receives a commission in the Reserve. A physician with recognized standing in a specialty such as medicine, surgery, radiology, otolaryngology, etc., is given the designation of MC-V(S) USNR, meaning Medical Corps Volunteer Specialist, U. S. Naval Reserve. The rank he receives on entering the service depends on his years of experience in his specialty, his standing therein, and his personal abilities. If he is not a qualified specialist his designation is MC-V(G) USNR, meaning Medical Corps Volunteer General, U. S. Naval Reserve. Again his rank is determined by his qualifications, experience, and abilities. Needless to say, most of the officers with the designation MC-V(G) USNR are the younger men who have graduated so recently that they have not become recognized specialists. There are other classes of reserve medical officers, as the organized reserves, i.e., medical reserve officers who belong to some organized naval reserve unit of the line of the Navy and may be called with that unit to active duty, and the MC-M, USNR, the M indicating that the medical officer has served as doctor aboard ship in the merchant service. There are, in addition, specialist units which have been organized throughout the country. Usually at some hospital or clinic a reserve medical officer of the rank of Lieutenant Commander or above acts as organizer of such a unit. These units consist of groups of specialists, an internist, surgeon, eye, ear, nose, and throat specialist, radiologist, orthopedic man, laboratory man, and psychiatrist, making up a typical unit. This group, headed by the organizer, who is a specialist and usually the senior man of the group, is assigned a number and becomes known as Specialist Unit No. —, whatever the number may be.