Intravesical Adriamycin treatment was given to 22 patients with carcinoma in situ of the urinary bladder. The treatment schedule consisted of monthly Adriamycin instillations in a dose related to bladder capacity. Endoscopic inspection with multiple bladder biopsies and cytoanalysis of urine was performed after every third instillation. In two patients there was lasting disappearance of the carcinoma in situ. Another 10 patients possibly had a beneficial effect of the treatment. The remaining 10 patients showed persistent malignancy and in 6 of these, progression of carcinoma in situ during Adriamycin treatment necessitated cystectomy or radiotherapy. The histologic and cytologic findings showed distinct variability in most patients, with atypia or even absence of malignant cells often followed by recurrence. Adriamycin was discontinued in four cases because of severe cystitis, and in one case because of an anaphylactoid reaction following instillation of the drug.