Alemtuzumab is active in chronic lymphocytic leukaemia (CLL) patients refractory to alkylators and fludarabine. The aim of this study was to determine the efficacy and safety of subcutaneous alemtuzumab at low dose (10 mg three times per week, for 18 weeks) to 49 patients with pre-treated CLL. The overall response rate was 53%, including 27% of complete responses; it was 42% in patients over 70 years, and 54% in the fludarabine-resistant patients. Forty-five percent of the patients with an unfavourable karyotype responded, including 60% of those with the 17p- aberration. After a median follow-up of 25 months, the median overall time to disease progression was 8 months (responders 12 months, non-responders 4 months). The median overall time to alternative treatment was 9 months (responders 17 months, non-responders 6 months) and median overall survival was 30 months. The treatment was well tolerated: grade IV neutropenia was observed in 17%, and cytomegalovirus (CMV) reactivation in 24% of the patients, with no CMV disease. We observed a total of 30 infections (50% during treatment and 50% during the 12-month follow-up), only one-third of which was severe. This study confirms that low-dose subcutaneous alemtuzumab is effective in poor prognosis CLL, and has a particularly favourable toxicity profile.