The humanized anti-CD52 monoclonal antibody alemtuzumab is an effective therapy for chronic lymphocytic leukemia (CLL). We examined the impact of alemtuzumab treatment after initial fludarabine treatment for feasibility and safety. Patients (N = 85) with previously untreated symptomatic CLL received fludarabine (25 mg/m(2)/day) for 5 days every 4 weeks for four cycles followed by 2 months of observation. Patients with stable disease or better response then received alemtuzumab 30 mg three times weekly for 6 weeks either intravenously (IV; cohort 1; N = 39) or subcutaneously (SC; cohort 2; N = 20). Of the 85 evaluable patients enrolled on our study, four (5%) attained a complete response (CR) and 43 (51%) attained a partial response after fludarabine induction for an overall response rate (ORR) of 55%. Thirty-nine patients received IV alemtuzumab for consolidation with improvement in CR to 27% and ORR to 73%. Twenty patients received SC alemtuzumab consolidation with improvement in CR to 17% and ORR to 69%. Toxicity from IV alemtuzumab included infusion-related reactions and infection. Mild local inflammation was common from SC alemtuzumab but there were virtually no systemic side effects. Nine of 59 (15%) patients had cytomegalovirus (CMV) infections; one patient died. The administration of alemtuzumab as consolidation therapy following an abbreviated fludarabine induction is feasible but requires close monitoring for CMV infection and other infectious events.