Hemophagocytic syndrome (HS) is a severe hyper inflammatory condition whose cardinal symptoms are prolonged fever, cytopenia, hepatosplenomegaly, and hemophagocytosis by activated, morphologically benign macrophages. The clinical course resembles sepsis, sharing similar physiopathological features. We report four patients with the syndrome. A 61-year-old female presenting with fever and pleuritic pain. During the course of the disease, a pancytopenia was detected and a bone marrow aspiration was suggestive of HS. The patient was treated with cyclosporine and steroids with a good response. A 61-year-old male with fever and pancytopenia and a bone marrow aspirate suggestive of HS. The patient did not respond to treatment and died. A 23-year-old male with fever, pancytopenia and positive Hanta virus antibodies. A bone marrow aspirate was suggestive of HS. The patient recovered without any treatment. A 72-year-old male admitted with the diagnosis of pneumonia, that developed a progressive pancytopenia and bone marrow aspirate was suggestive of HS. A bronchoalveolar lavage showed the presence of Acinetobacter baumanii. Despite treatment with methylprednisolone and gammaglobulin, the patient died. Awareness of the clinical symptoms and of the diagnostic criteria of HS is important to start life-saving therapy in time. (Rev Med Chile 2011; 139: 224-229).