Of 27 patients with the acquired immunodeficiency syndrome (AIDS) in Tucson, Arizona, 7 had concurrent coccidioidomycosis. Early manifestations of infection in 6 patients included diffuse nodular pulmonary infiltrates and Coccidioides immitis in many extrathoracic sites. By comparison, a retrospective review of the cases of 300 patients hospitalized with coccidioidal infection identified only 13 patients without AIDS who had the same extent of infection, and only 3 of these patients had no immunosuppressing conditions. Antibodies for coccidioidal antigens at serum dilutions as high as 1:2048 were detected in 5 of the 7 patients with AIDS. Six had temporary responses to amphotericin B treatment, taken both alone and combined with ketoconazole, but all died within 14 months of their diagnosis of coccidioidomycosis. Because annual rates of coccidioidal infection in the Tucson area are 4% or less, the rate of 27% that we calculated, based on 7 patients having the infection during 26 years of risk for AIDS, suggests frequent reactivation of the infection or enhanced susceptibility to endemic exposure in persons with AIDS.