To the Editor.
—On January 1,1992, the Centers for Disease Control (CDC) is expected to propose that a CD4+ T-lymphocyte cell count of 200 × 106 cells/L or less in a person seropositive for the human immunodeficiency virus (HIV), in the absence of other clinical findings, be added to the list of the acquired immunodeficiency syndrome (AIDS) defining conditions. Some of the consequences of this action can be estimated from data collected in the San Francisco (Calif) Men's Health Study and the San Francisco General Hospital Cohort. These cohorts comprise approximately 1250 homosexual and bisexual men recruited in 1983 and 1984 by a combination of sampling and volunteer procedures. Both cohorts have been examined regularly since recruitment and CD4+ T-lymphocyte counts have been determined at each examination.By the end of 1990,271 cases of AIDS meeting the 1987 criteria defined by the CDC had been diagnosed. If the proposed