Sixteen episodes of fungemia due to Coccidioides immitis were identified in 15 patients over a 7-year period at 2 hospital associated with the University of Arizona in Tucson. Fourteen of the 15 patients were male and 13 had an underlying condition, including malignancy in 6 and AIDS in 3. Ten of the patients were receiving corticosteroids at the time of fungemia. TP antibodies were present in 5 of 9 episodes and some titer of CF antibody was present in 7 of 11 instances. None of the 10 patients tested had a positive 1:100 coccidioidin skin test. In 11 of 15 episodes, a miliary chest roentgenographic pattern was apparent at the time of fungemia. Eleven of the 16 episodes ended in death within 1 month of the positive blood culture. Fungemic patients were compared to patients with culture-proven coccidioidomycosis without fungemia and differed from them significantly in 3 respects. First, fungemic patients were more likely to have a diffuse miliary pattern on chest radiograph. Second, all fungemic patients had, by definition, disseminated coccidioidomycosis and this was more likely among fungemic patients than among non-fungemic patients. Finally, fungemic patients were more likely to die within 1 month of the positive culture for C. immitis. Fungemia occurred in greater than 30% of patients with culture-proven coccidioidomycosis who had a blood culture performed. These results suggest that coccidioidal fungemia is a marker for a severe, acute form of disseminated coccidioidomycosis associated with a high mortality.