Epidermal growth factor (EGF), a mitogenic polypeptide with a molecular weight of 6000, is excreted in human urine in nanomolar quantities. Recently, some reports showed that urothelial neoplasm was related to the concentration of EGF in urine. In this study, EGF concentration in urine was measured by enzyme-linked immunosorbent assay (ELISA) in 207 samples from 112 male patients (30-90 years old, median 66.2) who had previously been treated for bladder cancer. Then, we tried to clarify the significance of urinary EGF as a marker for recurrence of bladder cancer in comparison with urine cytology. The samples were collected on occasional follow up cystoscopy. Urine from nine age-adjusted males without urological disease was also measured to obtain normal control values. In 123 samples from patients without tumors, EGF concentrations in urine decreased with age. In 84 samples obtained from patients with recurrent tumor, EGF concentrations were significantly lower than those in 123 samples from patients without tumors (P < 0.001) Furthermore, EGF concentrations in longitudinal samples collected the same patients during tumor recurrence and at the times when no tumor was detected were measured in 56 patients. EGF concentrations in the samples collected during tumor recurrence was significantly lower than that in specimens collected when there was no tumor (P < 0.01). There were no significant differences between the same samples collected during tumor recurrence with regard to tumor grade, stage shape and number of tumors. However, EGF concentration in urine from patients with carcinoma in situ (CIS) was lower than that in specimens from patients without CIS. These results indicate the usefulness of determining the EGF concentration as a marker for detecting bladder cancer recurrence. Urine cytology was also examined in the same series and findings were compared with those of urinary EGF. On cytology, class IV and V were considered positive, and on urinary EGF, less than 10 ng/mgCr were considered positive. Sensitivity was 25% for cytology and 57% for urinary EGF, while specificity was 98% and 66%, respectively. The predictive positive value was 0.88 and 0.53, respectively. With the combined use of urinary EGF and cytology, the sensitivity, specificity and predictive positive value were 68%, 64% and 0.92, respectively. In conclusion, urinary EGF seems to be a useful marker for detecting bladder cancer recurrence if performed in addition to cytology. cancer recurrence if performed in addition to cytology.