OBJECTIVE: To assess the feasibility and safety of diagnostic or therapeutic semirigid ureteroscopy without ureteral meatus dilatation. MATERIALS AND METHODS: A comparative, retrospective study was conducted of patients undergoing ureteroscopy from January 2000 to May 2008. For data analysis purposes, the population was divided into two groups based on whether ureteroscopy had been performed with (Group 1) or without (Group 2) ureteral meatus dilatation. Variables recorded included age, sex, type of procedure, surgical diagnosis, passive or active dilatation, number of stones, stone location, stone diameter, peroperative and postoperative complications, internal urinary diversion after the procedure, therapeutic success rate, operating time, and hospital stay duration. A 8-9.8 Fr Wolf semirigid ureteroscope was used. Descriptive statistics of the population and cohorts were performed, providing medians, quartiles, and limit values for non-normally distributed interval variables, and absolute and relative frequencies for categorical variables. Shapiro-Wilk's, Mann-Whitney's U, Chi-square, and Fisher's exact tests were used for statistical analysis. A value of p 2 alpha < or = 0.005 was considered statistically significant. Arcus Quickstat Biomedical 1.0 software was used. RESULTS: Among the 306 ureteroscopies studied, 286 performed in 256 patients were analyzed. Median age was 50 years (16-83), 59% of patients were male, and elective ureteroscopy was performed in 183 patients (64%). Group 1: 191 ureteroscopies, Group 2: 95 ureteroscopies. Stone location: 149 in distal ureter, 60 in middle ureter, and 35 in proximal ureter. Sixty-nine percent of stones had sizes ranging from 5 and 10 mm. The overall success rate was 86.5%. There were 5 peroperative and 22 postoperative complications, with no statistically significant differences between the groups. CONCLUSIONS: In selected cases, ureteroscopy may be performed without ureteral meatus dilatation with success and morbidity rates similar to when the procedure is performed with meatal dilatation.