In this series of 31 patients with acute infection due to human immunodeficiency virus (HIV) type 1, the male-to-female ratio was 3.4:1 and the mean age was 31.3 years. Sexual transmission accounted for 83.9% of cases; 45.2% of the patients were homosexual and 38.7% were heterosexual. The mean duration of symptoms and signs was 21 days (range, 5-60 days). Fever (87.1%) and skin rash (67.7%) were most commonly reported. Physical examination findings were abnormal for 96% of the patients; the oral cavity (76.7%) and the skin (73.3%) were the most frequently involved sites. Thirteen of 25 patients with sexually acquired infection had genital or oral ulcers, whereas five intravenous drug users had none (P = .052). Thrombocytopenia was the most common hematologic abnormality and was detected in 17 of 23 patients tested. P24 antigenemia, an initially negative screening test for HIV antibody, and a low CD4+ lymphocyte count were noted in 23 of 29, 23 of 30, and 14 of 21 tested patients, respectively.