We describe an 11-year-old boy with acute Q fever complicated by hemophagocytosis. In addition to pancytopenia, the boy presented with hyponatremia, hypofibrinogenemia, and changes in lipid metabolism. Examination of a bone marrow aspirate revealed striking hemophagocytosis. All of the pathological changes were caused by an activated macrophage system. We also discuss the possible role that pathogenetic mechanisms play in these changes.