A 49-year-old man with mantle cell lymphoma received 2.5 g/m2 of cyclophosphamide and 900 mg/m2 of etoposide followed by 10 microg/kg/day of Filgrastim for PBPC mobilization. This was complicated by marked hyperleukocytosis and retinal hemorrhages. The patient's symptoms improved gradually following leukopheresis. To the best of our knowledge, this is the first report describing this complication in patients undergoing PBPC mobilization. Early recognition of symptoms is important in order to stop Filgrastim and initiate immediate leukapheresis.