Papillary transitional cell carcinoma of the bladder (PTCCB) is characterized by a high recurrence rate with infiltration of bladder wall and surrounding tissues. The outcome is poor in 10-20% of the cases and these cannot be detected by conventional methods. Different methods have been utilized to identify this high risk patient group, such as the tumor growth factor (TGF). This is obtained with the KI-67 antibody, which identifies a nuclear protein in the cells in the active cellular cycle (G1, G2, S and mitosis). TGF represents the percentage of KI-67 positive tumor cells. The aims of the present study were: 1) to determine the correlation of the histological features and TGF in PTCCB; 2) to determine the percentage, if any, of superficial low grade lesions with a high TGF. Thirty-one transurethral biopsies of patients with PTCCB were analyzed to determine the histological grade (following the criteria described by Ash), wall infiltration (according to the IUAC criteria) and TGF (using the PAP technique). The study revealed 16 (52%) were low grade and 15 (48%) were high grade tumors, 20 (64.5%) were superficial (PTa-PT1), 9 (29%) were deep (PT1-PT4) and the degree of wall infiltration could not be determined in two cases. Of the 20 superficial tumors, 15 (75%) had a low (0-15%) and 5 (25%) had a high (> or = 16%) TGF. The 9 cases with deep infiltration of the bladder wall (PT2-PT4) had a high TGF.(ABSTRACT TRUNCATED AT 250 WORDS)