The editorial committee for the Annual Review has carefully selected in-depth monographs on subjects of present medical interest for presentation. The text is divided by specialty and includes clinical pharmacology, genetics, obstetrics, psychiatry, and public health, in addition to the traditional subdivisions of internal medicine. Because of this diversity and the very specific nature of each review, it is necessary for the reader to scrutinize the contents carefully in order to choose for study those subjects of pertinence to his specific needs. I find it difficult to believe that a single reader will have an in-depth interest in both "Estimation of Gestational Age in the Fetal State" and "Endogenous Carbon Monoxide Metabolism." In recognition of this selectivity by the reader, the editorial committee has indexed each contribution by a number aligned in the margin of the title page for use in the direct order of reprints of the specific review.