One hundred five asymptomatic human immunodeficiency virus-seropositive adults were screened for measles antibody. Ages ranged from 21 to 59 years (mean, 35.7). CD4 + lymphocyte counts (range, 76-1137/mm 3 ), percentage of CD4 + cells (6-42), CD4:CD8 ratio (0.08-1.3), measles antibody titers by EIA, and undocumented history of prior measles or immunization were obtained. Forty-six patients gave a history of measles but no immunization, 18 of immunization but no measles, 26 of immunization and measles, and 15 of neither measles nor vaccination. Only one patient (<1%) lacked levels of antibody considered protective. Neither the presence nor the level of antibody were predictable from patient age, history of measles or immunization, CD4 + lymphocyte count, percentage of CD4 + cells, or CD4:CD8 ratio. Nearly all subjects had antibody to measles, regardless of immunization or measles history. Whether these antibodies are truly protective is unknown.