This is the first report of a case of a reduction in kidney volume and preservation of renal function in a patient with autosomal-dominant polycystic kidney disease (ADPKD) receiving rapamycin. A 42-year-old man with ADPKD and a severe persistent bleeding from his solitary left kidney was successfully treated with tranexamic acid (TXA). He also received low-dose rapamycin for 8 months, and this was associated with a 23.5% reduction in kidney volume, improvement and stabilization of renal function, and normalization of haemoglobin levels. When treatment with rapamycin was interrupted, renal function deteriorated within an 8-month period and haemodialysis (HD) became necessary. Kidney volume increased at once, and life-threatening bleeding prompted a nephrectomy 4 months after the onset of HD. These data suggest that the reduction in kidney volume and preservation of renal function with rapamycin could be the result of the antiangiogenic, antiproliferative effects of rapamycin.