46 ambulatory patients with chronic lymphocytic leukemia were treated with Prednimustine either continuously (daily or each other day 20 mg) or intermittently (daily 20 mg for 14 days, followed by a pause of 4 weeks). A good response was seen in 28 patients lasting up to 17 + months (mean 4,5 + months) after terminating therapy. Patients without prior chemotherapy have improved earlier and to a smaller amount of the total dose applicated. Signes of bone marrow toxicity (anaemia, thrombocytopenia) were observed in 8 cases, gastrointestinal side effects in 7 cases, cutaneous exanthema in 3 cases, and one patient exhibited a severe stomatitis after treatment. Prednimustine constitutes an effective drug for chronic lymphatic leukemia.