We report on 10 kidney transplant patients with acute hemorrhagic cystitis caused by adenovirus, accompanied by the deterioration of kidney function. They developed macrohematuria with urgency, frequency and micturition pain for more than 7 days within 1 year after transplantation. Adenovirus type 11 was isolated from the urine of 6 patients, and complement-fixing antibody became positive in 9 patients. Hematuria and irritative voiding symptoms disappeared without any specific treatment; however, serum creatinine rapidly increased. The histological findings of the biopsy specimens indicated that renal impairment was attributed to acute rejection in some cases and virus-associated nephropathy in other cases. Acute hemorrhagic cystitis caused by adenovirus is an interesting complication after kidney transplantation, especially with regard to kidney impairment and treatment.