One hundred seventeen patients with mycosis fungoides were treated with topical mechlorethamine hydrochloride. The probability of achieving a clinically apparent remission within 2 years of therapy was 75.8% in patients with stage I disease, 44.6% in patients with stage II disease, and 48.6% in patients with stage III disease. Patients with stage I disease achieved complete remission sooner (median, 6.5 months) than patients with stage II (median, 41.1 months) or stage III (median, 39.1 months) disease. The median time to relapse was 44.5 months. Sixty-eight patients (58.1%) developed a delayed hypersensitivity reaction, but only one patient had to discontinue therapy as a consequence. No appreciable differences were seen in the probability to achieve complete remission or time to complete remission as stratified by gender, substage, or the development of a delayed hypersensitivity reaction. Survival analysis revealed that the probability of surviving at 5 years was 89% for all patients. These findings compare favorably with results with other treatments for early stage mycosis fungoides.