Alemtuzumab is usually associated with opportunistic infections. We have treated 67 patients, 8 non-Hodgkin's lymphoma and 59 chronic lymphocytic leukemia (CLL) with campath. Among CLL patients, 6 used alemtuzumab in first line, alone or with chemotherapy, 41 as consolidation therapy and 11 as salvage therapy, 3 alone and 8 with chemotherapy. In our series opportunistic infections were prevalently found in patients submitted to alemtuzumab salvage therapy (33.3%), with or without chemotherapy; in particular 1 pulmonary nocardiosis, 1 tubercolosis. Also during the first line alemtuzumab therapy one case of lysteriosis and one case of HBV reactivation were found (33.3%). No opportunistic infections were diagnosed to our CLL patients in consolidation therapy, when the underlying hematologic disease was reduced or present only as minimal residual disease. A good response of malignancy, namely CLL, to induction therapy, such as a less aggressive schedule of therapy, determine a lower risk of immunosuppression and therefore a low number of opportunistic infections.