We conducted a retrospective study to determine the prognostic significance of age, gender, associated carcinoma in situ, stage, number of tumors, and tumor size for patients with high-risk non-muscle-invasive bladder tumors treated with bacillus Calmette-Guérin (BCG). Data were evaluated on 144 high-risk patients with non-muscle-invasive bladder cancer treated with BCG immunotherapy after the initial treatment with transurethral resection. According to their response to BCG, patients were divided into groups, and the differences in factors, associated with recurrence and progression, were evaluated. Patients were categorized into two groups: group A, complete responders without recurrence and without progression, and group B, patients with recurrence and with progression. Furthermore, group B was divided into two subgroups: group B1, patients with recurrence, and group B2, patients with progression. Univariate analysis of group B showed that only tumor size of >3 cm diameter (hazard ratio (HR) 11.99; 95% confidence interval (CI) range 5.69-25.3; p < 0.001) is associated with recurrence. After multivariate analysis, the same factor appeared to be prognostic for recurrence as well. In addition, group B2 was statistically correlated with group B1. Univariate analysis proved that tumor stage (Ta or T1) is the unique factor associated with progression (HR 6.4; 95% CI 1.29-31.9; p = 0.02). Tumor stage seems to be associated with disease's progression after the multivariate analysis too. Tumor size and stage may serve as prognostic factors, because of its independent correlation with recurrence and progression for patients with high-risk non-muscle-invasive bladder tumors treated with BCG.