BACKGROUND: Urinary retention is the most common complication after perianal surgery. The authors tried to evaluate the influence of the types and duration of the operation and the types of anesthesia on the incidence of urinary retention. METHODS: The medical and anesthetic records of 106 patients were reviewed retrospectively. They got perianal surgerys after recieving one of the regional blocks; 0.5% hyperbaric bupivacaine 5~8 mg intrathecally, 0.5% hyperbaric tetracaine 5~8 mg intrathecally, or 2% lidocaine 300 mg with epinephrine 5 g/ml caudally. The incidences of urinary retention were compared with each other by Chi-square test and Student t-test, according to the above mentioned points. RESULTS: Fifty percent of these patients underwent urinary catheterization. The incidence of urinary retention after hemorrhoidectomy (56.6%) was higher than that of other anorectal procedures (p<0.05, Chi-square test). The longer operating time was associated with urinary retention (p<0.05, Student t-test). The influence of local anesthetics (bupivacaine, tetracaine, and lidocaine) was absent (p>0.05, Chi-square test), but the difference between spinal and caudal anesthesia was slightly significant (p<0.05, Chi-square test), i.e. the incidence of urinary retention after caudal anesthesia was low. CONCLUSIONS: Short duration of operation, less traumatized perianal surgery, and caudal anesthesia are thought to lead to the lower incidence of urinary retention.