Transient suppression of hematopoietic colony formation from cytokine mobilized PBSC was observed in a patient following local radiation therapy for lymphoma. This effect was seen 2 weeks after completion of radiation and reversed by 6 weeks. The patient successfully engrafted after myeloablative chemotherapy with harvested PBSC. This report documents the first reported case of suppression of PBSC colony formation following radiation and we speculate that this finding may be due to an abscopal effect.