OBJECTIVE To evaluate the natural history and the efficacy of treatments for carcinoma in situ (CIS) of the urinary bladder, we reviewed 70 patients with this disease. METHODS The patients of CIS were divided into 3 groups based on tumor history: primary, secondary and concurrent CIS. We studied 70 patients with primary and secondary CIS treated at our hospital between 1957 and 1995, exclusive of concurrent one. They included 31 patients with primary CIS and 39 with secondary one, ranging in age from 39 to 82, with the average age of 63.1 years. Sixty-one patients were male and 9 were female. RESULTS In 31 patients with primary CIS, 12 (32.8%) complained of gross hematuria, 10 (32.3%) urinary frequency and 9 (29.0%) pain on urination. The 5-year survival rates for primary and secondary CIS were 89.1% and 91.4%, and the 5-year bladder preservation rates were 54.5% and 57.6%, respectively. Three of 31 patients with primary CIS developed an invasive carcinoma, whereas 4 of 39 patients with secondary CIS did. There was no significant difference between each primary and secondary groups. In both primary and secondary CIS, the group of immediate total cystectomy was not significantly differ from the groups of the following total cystectomy and the bladder preservation in the effect of total cystectomy on the survival rate. A total of 51 cases of CIS was treated with intravesical therapy, 17 intravesical Bacillus Calmette-Guérin (BCG) therapy, 34 intravesical chemotherapy, respectively. Intravesical BCG therapy has shown the complete response rate of 78.6%, intravesical chemotherapy 42.1%. And the bladder preservation rate seemed to be better (but not significantly) in intravesical BCG group than in intravesical chemotherapy group or non-treatment group of intravesical therapy. CONCLUSIONS For both primary and secondary CIS, the 5-year survival rate was about 90% and 5-year bladder preservation rate was over 50%. There was no significant difference between the primary and secondary group. The group of immediate total cystectomy was not significantly differ from the groups of the following total cystectomy and the bladder preservation in the effect of total cystectomy on the survival rate. About intravesical therapy, BCG was very effective in CR rate and the bladder preservation rate seemed to be better (but not significantly) in BCG group than in chemotherapy or non-treatment group.