There have been few reported cases of ureteral diverticula less than 4 mm in diameter; these are best described as pseudodiverticula based on their appearance in specimens obtained for pathologic study. An additional 23 patients are reported, 15 of whom were examined by urinalysis, urine culture, cystoscopy, and cytologic studies of the urine. Cytologic findings are of interest because of previous reports suggesting an association between ureteral diverticula and transitional cell carcinoma in the urinary tract. Hematuria, transitional cell carcinoma, and benign prostatic hyperplasia were the most common presenting conditions. Infection was found in only three. Diverticula were multiple in 91%, bilateral in 69%, and were predominantly upper and midureteral in location. Urine cytologic studies failed to detect early uroepithelial malignancy, but nonspecific cellular atypia and an association with malignancy in 30% of these patients suggests that close follow-up of patients with ureteral pseudodiverticulosis is prudent.