According to cell cycle synchrony principles, bleomycin was infused for 48 hours, followed by a dose of either methotrexate or hydroxyurea after a 24-hour rest, in 36 adult patients with disseminated carcinoma. In this preliminary study, a 59% response rate was noted among patients with epidermoid carcinoma of the head and neck. Four of four patients with transitional cell carcinoma of bladder and one patient with hypernephroma also responded. No responses were noted among five patients with epidermoid carcinoma of the lung. The length of response ranged from 1 to 8 months (median, 2 months). Seventy-seven percent of the responders had extensive prior radiotherapy. The first patient treated had fatal sepsis with leukopenia, which prompted a widening of the treatment interval. Subsequently, toxicity was mainly mild or absent, the moderate or severe toxicity was primarily neutropenia, which was reversible. The use of low-dose bleomycin infusion is safe and may play a role in cancer therapy in combination with other agents specific for certain tumors. The length of infusion should be determined by the cell cycle of the tumor, if its potential synchronizing capabilities are to be exploited.