The production and mRNA expression of the cytokines interferon-gamma (IFN-gamma) and interleukin (IL)-4, -10, and -12 by peripheral blood mononuclear cells (PBMC) after incubation with the coccidioidal antigen toluene spherule lysate (TSL) from various subjects were measured. The IFN-gamma concentration in PBMC supernatants incubated for 72 h from 8 subjects with disseminated coccidioidomycosis was significantly less than that from 7 healthy, coccidioidal-immune subjects (P = .015). No differences were seen among the subject groups in the concentrations of IL-4, -10, or -12. By use of competitive polymerase chain reaction, PBMC from subjects with disseminated coccidioidomycosis also expressed less mRNA for IFN-gamma and IL-12 than did cells from healthy, immune subjects. These data suggest that patients with disseminated coccidioidomycosis have a diminished T helper lymphocyte type 1 response.