Purpose: To assess the activity and side effects of cladribine (2-CdA) treatment in patients with advanced Waldenström's disease. Patients and methods: Ten symptomatic patients without prior therapy were included in a prospective multicenter trial. 2-CdA was administered daily at 0.12 mg/kg body weight in a 2-h i.v. infusion over 5 consecutive days; this was repeated every 28 days for four cycles. Patients achieving a remission received interferon alfa-2c (IF) 15 μg s.c. three times a week for 1 year. Results: All 10 patients responded to 2-CdA (100%; 95% confidence interval, 68–100%), with one complete (CR) and eight partial responders (PR); one patient had only one 2-CdA cycle and showed a minor improvement (MR). Patients tolerated the treatment well. Despite considerable immunosuppression, an infection occurred in only two patients. After a median observation period of 57 weeks, three patients had shown progression, including one who died of lymphoma. Conclusion: 2-CdA induction and IF maintenance is a well-tolerated therapy for symptomatic untreated patients with advanced Waldenström's disease and offers excellent palliation.