To study maintenance Bacillus Calmette-Guérin (BCG) therapy we treated 49 patients with recurrent superficial bladder cancer pTa and/or carcinoma in situ, failing previous intravesical chemotherapy. They received 20 intravesical instillations in 1 year, with or without 6 intradermal inoculations. Side effects were frequent, causing treatment stop in 14 patients (29%). Drug-induced cystitis was the most frequent side effect, seen in 29 patients (59%). Forty-two patients were evaluable for response. During the first 2 years of the study 14 patients (33%) had one (n = 8) or more (n = 6) recurrences. A total of 18 patients (43%) remained recurrence free with a median follow-up of 47 months. Progression was seen in 2 patients from pTa to pT1, another patient died of metastatic bladder cancer after 47 months. PPD skin test conversion was of no prognostic value. The use of intradermal inoculations caused no significant increase of toxicity and had no effect on efficacy, however, both groups were small. It caused no local side effects. We conclude that maintenance BCG therapy can be useful for patients with recurrent superficial bladder cancer failing previous intravesical chemotherapy.