During 1991, reported cases of coccidioidomycosis (i.e., valley fever) in California increased more than three-fold over the annual number of cases reported since 1986; during 1992, the number of reported cases increased 10-fold. Coccidioidomycosis, a fungal disease caused by Coccidioides immitis, is endemic in certain parts of Arizona, California, Nevada, New Mexico, Texas, and Utah. Sporadic cases occur each year in parts of the United States in which the disease is not endemic and may present diagnostic difficulties and laboratory hazards because health-care workers may be unfamiliar with coccidioidomycosis. Recent increases in California and reports of isolated cases in areas without endemic disease suggest that physicians and laboratory personnel should be alert to the possible role of C. immitis. This report summarizes the occurrence of coccidioidomycosis in California during 1991 and 1992 and highlights three cases that occurred in areas in which the disease is not endemic.