32 patients with bladder carcinoma in situ (CIS) were treated by intravesical instillations of BCG immun F Pasteur between 1988 and 1991. The CIS was isolated (13 cases, 40.6%) or associated with a pTa papillary tumour (10 cases, 31.2%), pT1 tumour (8 cases, 25.1%) or pT2 tumour (1 case, 3.1%). The protocol consisted of a series of weekly instillations of 150 mg of BCG for 6 weeks, repeated once in the case of persistent lesions on the first endoscopic follow-up examination. Patients were reviewed in the outpatients department every 3 months for 1 year, then every 6 months for 2 years in the absence of recurrence. Follow-up consisted of clinical examination, urine cytology and histology. The overall success rate, defined by complete resolution of the cytological and histological lesions for the total population was 81.25% (25/32) with a mean follow-up of 22.5 months. 18.75% (6/32) of cases were considered to be failures. Complications of treatment were observed in 59% of patients, but only required discontinuation of instillations in five patients (15.6%). In conclusion, intravesical BCG is the treatment of choice of bladder carcinoma in situ in the absence of detrusor invasion and contraindications to BCG.