Over the years, studies have been carried out on the epidemiology of fungal, bacterial and viral infections. These studies both retrospective and prospective whose main objective is to provide, on large series of patients, answers to the scientific world about the incidence and treatment of infectious complications in the hematological malignancy patients. We were also performed post-marketing studies of anti-infective drugs in order to confirm in “real life” results obtained in pivotal trials. The SEIFEM, to have a full scientific and academic autonomy, has never engaged in studies sponsored by Pharmaceutical Industry, however, it has remained appreciably to our side. The working group is open to all Italian and foreign centers who make a request for participation in our work. All studies comply with the Good Clinical Practice criteria and are always performed only after the approval of the Ethics Committees.