We retrospectively investigated the therapeutic outcomes of our series of 7 Ta and 62 T1 bladder cancers with grade 3 (G3) malignancy in 61 men and 8 women having a mean age of 66.2 years. Following transurethral resection of bladder tumor (TURBT), 35 and 6 patients received intravesical instillations of bacillus Calmette-Guerin (BCG) and anthracycline-derivants, respectively, whereas 15 received no adjuvant therapy. Five and 2 patients received systemic and local chemotherapy with irradiation, respectively, and six underwent radical cystectomy for invasive potential. The 5-year nonrecurrence, progression-free, and overall (cancer-specific) survival rates were 66, 82%, and 76 (88%), respectively, after a median follow-up of 52 months. The 5-year non-recurrence rates were 24% in non-adjuvant, 85% in BCG, 0% in anthracycline-derivants, 65% in systemic and local chemoradiation therapy, and 68% in cystectomy. The 5-year progression-free and overall (cancer-specific) survival rates of the patients treated with BCG instillation were 91% and 94 (100)%. There were no significant differences in the 5-year non-recurrence and progression-free rates between 12 patients with carcinoma in situ (CIS) and 23 patients without CIS. Complete TUR of all visible tumors and a reliable histopathological diagnosis of appropriate specimens bearing the muscle layer are mandatory for assessment of recurrence. G3 Ta-1 bladder cancers and CIS showed a high risk of recurrence, and required aggressive treatment. Since BCG therapy following TURBT significantly reduced the risk of recurrence and progression, adjuvant BCG therapy is considered to be the most promising initial conservative treatment for G3 Ta-1 bladder cancers.