The natural history of medical subspecialties.

Factors that have favored the division of the field of internal medicine into numerous subspecialties during the past three decades are reviewed. Some specialty areas are suited almost exclusively to academic clinical investigators, whereas others can be the basis for private practice. Some requisites for viability as a practice subspecialty are listed. It is suggested that in the coming decade the pendulum of preference is likely to swing back somewhat, with a larger fraction of young internists choosing to be identified as practicing general internal medicine rather than limiting their work to a single subspecialty.