Local recurrences of superficial transitional cell carcinoma of the bladder (TCCB) can be significantly reduced by intravesical treatment following transurethral resection (TUR) but they are not fully abolished. There is a need to gain experience with new agents. Anthracyclines, such as doxorubicin and epirubicin, have been clearly demonstrated to be active against superficial TCCB by intravesical route. Idarubicin is an anthracycline, much more lipophilic than doxorubicin, inhibiting tumour cell growth at lower concentrations. The aim of this study was to evaluate the tolerability and the ablative efficacy on a marker lesion of weekly intravesical instillations of idarubicin given at different doses and concentrations. Seventeen patients, affected by superficial TCCB, Ta-T1 G1-G2, after TUR of all tumours except one, that was used as a 'marker lesion', were treated intravesically with idarubicin weekly for two months. The drug, in the first 4 patients, was administered at the dose of 15 mg diluted in 30 mi of normal saline solution and maintained in the bladder for one hour. Because of severe chemical cystitis, the dose was reduced to 10 mg in 40 mi in the following 13 patients. The study was closed because of the severe local toxicity. In eight (47%) patients the treatment was interrupted for local toxicity between the first and sixth week and in 5 more patients pharmacological therapy was required because of severe chemical cystitis. No systemic toxicity was evident. Three patients achieved a complete response. Our experience shows that idarubicin is not indicated in the intravesical therapy of superficial TCCB because of severe chemical cystitis limiting the administration of doses able to explicate a relevant antitumoral action.