A unique case of adult-onset synchronous cyclic neutropenia and thrombocytopenia occurring at six-week intervals is presented. Periods of cytopenia were associated with fever, myalgias, gastrointestinal symptoms, and mild mucocutaneous bleeding. Alternate-day steroid treatment failed to correct the periodic fluctuations in peripheral blood counts but ameliorated symptoms during cytopenia. The treatment of cyclic hematopoiesis is reviewed.