A prospective, controlled study of surgical adjuvant immunotherapy with intralymphatic methanol-extractable residue (MER) of bacillus Calmette-Guerin (BCG) is preliminarily reported in 25 consecutive patients with high-risk malignant melanoma of the extremities. Patients were allocated on a random basis to receive preoperative intralymphatic immunotherapy with MER-BCG, surgical excision with regional lymphadenectomy and intraoperative infiltration of MER-BCG, and postoperative monthly intradermal vaccinations with BCG; or surgery and lymphadenectomy alone. Twenty patients followed for more than 1 year are the basis of this report. Fifteen patients accepted randomization, whereas four patients entered the immunotherapy group and one entered the control group at their own insistence. Immunotherapy improved the disease-free survival of patients in this trial. There was one recurrence with death in the 13 patients treated with preoperative intralymphatic MER-BCG; whereas four of seven patients in the control group had recurrence (P = 0.015), at all four of these patients died during the same interval.