Alemtuzumab, the monoclonal anti-CD52 antibody, has clinical activity in B-cell and T-cell malignancies at the dose of 30 mg three times weekly for 9-12 weeks. This standard regimen induced responses usually shorter than 6 months. To prolong time to progression, we initialized a phase II study with an identical initial scheme until partial response, followed by a maintenance therapy lasting at least 4 months. Eleven heavily pretreated patients (8 with B-chronic lymhocytic leukemia (B-CLL) and 3 with small lymphoctyic lymphoma (SLL)) have been treated with this maintenance regimen (MR patients) and were retrospectively compared to 5 patients (3 B-CLL and 2 SLL) treated with the standard regimen (SR patients). Patients characteristics before treatment were identical in both groups. Objective response was reached by 9 (82%) MR patients and 3 (60%) SR patients (p NS). After the treatment, 8 (73%) MR patients and all SR patients progressed with a median time at 12.2 months and 3 months respectively. Survival time from alemtuzumab was significatively different (P < 0.005). None of the patients died in the MR group with a median follow-up at 16 months. In the SR group, the median survival from alemtuzumab was 5.9 months. We did not observe any differences in terms of hematological toxicites and infections between the two groups. In conclusion, maintenance alemtuzumab therapy seems to increase the time to progression and the survival, without adding hematological toxicities and infectious complications. More patients are needed to confirm this observation.