['Quantify and study cofactors of long-term survival without AIDS in HIV-1-infected individuals with CD4+ cell counts < 200 x 10(6)/l.', 'Comparison of 579 participants who could be longitudinally evaluated for at least 3 years after the earliest date of first reaching a CD4+ cell count < 200 x 10(6)/l or an AIDS-defining illness (1987 Centers for Disease Control and Prevention definition).', 'Ongoing 9-year cohort study with data collected at 6-month intervals.', 'HIV-1-infected homosexual men.', 'Of the men, 20% did not develop an AIDS illness within 3 years following a confirmed CD4+ cell count < 200 x 10(6)/l; 29 and 28% were diagnosed with a first clinical AIDS illness from 1-3 and < 1 years, respectively, beyond their first CD4+ cell count < 200 x 10(6)/l; 23% were diagnosed with a clinical AIDS illness prior to their first CD4+ cell count < 200 x 10(6)/l. Slower decline of CD4+ cell count (P < 0.001) and presence of higher body-mass index during the period prior to the first CD4+ cell count < 200 x 10(6)/l (P < 0.001) predicted longer time to an AIDS illness once this threshold was reached. Most men had rapid loss of CD4+ cells, total T cells, and hemoglobin during the period after CD4+ cells declined below 200 x 10(6)/l. However, those remaining free of AIDS illnesses the longest arrested their decline in CD4+ cell counts and hemoglobin levels and increased total T cells during this period. Although antiretroviral therapy and Pneumocystis carinii prophylaxis extend AIDS-free survival, 45% of the group who were AIDS-free > or = 3 years after CD4+ cells fell below 200 x 10(6)/l had not used these treatments.'] Do long-term survival without clinical AIDS after CD4+ cell counts fall below 200 x 10 ( 6 ) /l?