A 47-year-old man with end-stage renal disease due to diabetic nephropathy underwent a peritoneal scintigraphy to evaluate the cause of recently developed scrotal swelling. Two liters of dialysate mixed with 111 MBq of Tc-99m sulfur colloid were administered into the peritoneal cavity via the dialysis catheter. Various anterior images of the abdomen and pelvis were obtained at 15 min, 2 hr and 4 hr after the tracer instillation. At 15 min, anterior images of the abdomen and pelvis demonstrated linear tracts of activity through both inguinal canals, which were more prominent in the right side (A). Images at 2 hr revealed a passage of the radioactive fluid into the right hemiscrotum. At the same time, there was a considerable accumulation of activity in the right inguinal canal (B). In the delayed image, there was a progressive accumulation of activity in the inguinal canals and a prominent passage of the tracer into the scrotum (C). Both abdominal and inguinal hernias are commonly associated with continuous ambulatory peritoneal dialysis (CAPD). Overall incidence of CAPD- induced hernia ranges from 2.7% to 25%.1) Inguinal hernias were frequently manifested as scrotal swelling. Leakages of dialysate fluid into the scrotum has been noted in CAPD patients with scrotal swelling, with or without clinical findings of inguinal hernia.1,2) In the present case, the right side had leakage from a clinical inguinal hernia and the left side, leakage from a subclinial inguinal hernia. A subclinical inguinal hernia was easily demonstrable with peritoneal scintigraphy. Peritoneal scintigraphy is extremely helpful in the evaluation of scrotal swelling in a patient on CAPD. (Korean J Nucl Med 2001;35:81-82)