The tumors in 249 patients presenting initially with stages Ta and T1 bladder cancer were analyzed for tumor progression and recurrence. Only transurethral resection and/or fulguration was used before the first recurrence. Patients who received intravesical chemotherapy after the first tumor recurrence were excluded from an analysis of progression. Progression according to stages Ta and T1, and grades I, II and III was 4, 30, 2, 11 and 45 per cent, respectively. All differences were statistically significant. Progression also correlated with nontumor dysplasia and size. High tumor grade, lamina propria invasion, atypia elsewhere in the bladder, positive urinary cytology, tumor multiplicity and large tumors were associated with shorter intervals free of disease.