A 31-year-old woman working in the laboratory with the mycelial phase of Coccidioides immitis developed a firm, raised, erythematous lesion on the left index finger. A biopsy specimen of the lesion grew a white mold that proved to be C immitis. A sinus tract communicating with the lesion and extending into the proximal phalanx developed. The expressed pus was positive for the tissue form of C immitis by potassium hydroxide and periodic acid-Schiff stains and fluorescent-antibody techniques. The sinus tract was irrigated with an aqueous solution of amphotericin B (Fungizone). The tract closed and the lesion decreased in size. Healing was completed in ten weeks. Primary cutaneous disease must be distinguished from disseminated disease with cutaneous manifestations. In the majority of cases, primary disease heals spontaneously whereas disseminated disease usually requires systemic treatment with amphotericin B.