A cohort of anti-human immunodeficiency virus (HIV) positive donors and controls has been under prospective followup since 1985 (N Engl J Med 321:917, 1989). The cohort is now in its 16th year of followup. At enrollment, 182 subjects were Western blot (WB) positive, including 158 asymptomatic donors, 15 blood recipients, and 9 sexual partners. A control population included 70 anti-HIV reactive donors who were WB negative and 21 who were WB indeterminate. Of the 182 WB-positive subjects, 87 percent were donors, 5 percent sexual partners, and 8 percent recipients. Of the 182 WB positives, 49 are alive and in active followup; 58 (32 percent) are dead, of whom 54 (93 percent) died of AIDS; 75 (41 percent) are lost to followup (LTFU). We suspect most LTFU have succumbed to AIDS, but need access to the National Death Index to establish this: 13 of the 73 LTFU were known to have AIDS at the time they left the study. Of the 51 in active followup, 40 (75 percent) are males and 49 (92 percent) were detected at blood donation. Nineteen of the 51 (37 percent) have had an AIDS defining event. Others have CD4 counts under 300, but have had a stable course even before treatment. A subset of 13 patients have exceeded 10 years of followup and have CD4 counts persistently more than 400 with no AIDS-defining infections and no physical abnormalities except minor adenopathy. Our goal will be to focus on this group in terms of predictive factors for long-term non-progression. AIDS or HIV-related phenomena have not developed in any of the 21 WB-indeterminate or 70 WB-negative subjects. Treatment with HAART therapy is being conducted by personal physicians or through other NIH protocols.