A 79-year-old man developed a high fever, facial erythema, anemia and thrombocytopenia during conservative therapy for ischemic colitis. Peripheral hemophagocytes (PHP) were identified in smear specimens of peripheral blood, and hemophagocytes also showed proliferation in the bone marrow. After treatment with steroid and antibiotics under a diagnosis of bacteria-associated hemophagocytic syndrome, the patient recovered rapidly. Although the prognosis of hemophagocytic syndrome (HPS) depends on the underlying disease, any delay in diagnosis can sometimes result in a poor outcome in cases of infection-associated hemophagocytic syndrome. In the present case, early diagnosis of bacteria-associated hemophagocytic syndrome was made by detection of PHP. The appearance of PHP in virus-associated hemophagocytic syndrome (VAHS) and after administration of macrophage colony stimulating factor has been described. However, the significance and cytological characteristics of PHP have been unknown. In this report, we propose that PHP can be a useful indicator for early diagnosis of HPS, and we report 7 additional cases in which the PHP was detected retrospectively. The cytological characteristics and biological significance of PHP are discussed.