Primary hemophagocytic syndromes represent a group of rare immunodeficiencies, which are characterized by development of life-threatening systemic inflammatory manifestations, so-called accelerated phases. Immunosuppressive therapies are only temporarily effective to control this complication and the prognosis is dismal unless treated by hematopoietic SCT (HSCT). At present, optimal modalities of this potentially curative approach remain incompletely defined. In this study, we analyzed our experience in 18 patients with primary hemophagocytic syndromes treated since 1984 in our center by HSCT. Ten of these patients had previously developed accelerated phases and were in remission at the time of HSCT, whereas five patients had findings of active disease, with two cases in early phases of recurrences of less than 2 weeks duration and three cases with persistent central nervous system disease, whereas three patients had never experienced accelerated phases. In the group with active disease, four of five patients are long-term survivors and are well, whereas one patient died of CMV pneumonia. This outcome compares favorably with results in patients transplanted in remission, where 6 of 10 are long-term survivors. Our findings indicate that HSCT can have a favorable prognosis even in patients with active disease of primary hemophagocytic syndrome.