A 37-year-old male presented with primary plasma cell leukemia (PCL) with kappa-type Bence Jones proteinuria (BJP) and polyposis of the stomach and colon. His plasma cell leukemia was not preceded by a pre-existing multiple myeloma, and presented the complication of polyposis in both stomach and colon. Biopsy of mucosal lesions revealed marked accumulation of atypical plasma cells with positive cytoplasmic kappa-chain. No amyloidosis was present. His disease responded remarkably well to intermittent melphalan and prednisolone. This case represents an uncommon combination of primary plasma cell leukemia and polypoid gastrointestinal lesions with plasma cell infiltration.