A multicentric randomised trial was conducted for the purpose of investigating the efficacy of intravesical chemoprophylaxis of superficial bladder cancers. A total of 443 patients (number of evaluable patients, 284) were registered from July 1987 to December 1989 and randomised into 3 groups. Group A received 21 intravesical instillations of Adriamycin (ADM) at 20 mg/40 ml physiological saline for 2 years after undergoing transurethral resection (TUR); group B was given the same dose as group A but received 6 intravesical instillations for 2 weeks before undergoing TUR; and group C served as a control and underwent TUR only. Better prophylactic effects were obtained in group A. The overall non-recurrence rates calculated for groups A and B differed significantly (P less than 0.05) on day 240, and those determined for groups A and C were also significantly different (P less than 0.01) on day 480. No benefit was obtained using intravesical instillation prior to TUR (group B). The major side effects encountered were pollakisuria and miction pain, which occurred in 32% of the patients in group A and in 52% of those in group B.