A previously unreported complication of low anterior resection of the rectum, seminal vesicle-rectal fistula, was encountered one month after surgery in an elderly patient with adenocarcinoma of the midrectum. Antibiotic-induced colitis in the immediate postoperative period led to anastomotic leakage with abscess formation and ensuing fistulization to the surgically denuded right seminal vesicle. Pneumaturia, bacteriuria, and right testicular pain were treated by cutaneous vasostomy and antimicrobial therapy. Despite recurrent low-grade urinary sepsis controlled by alternating courses of various antimicrobials, and radiation therapy for local tumor recurrence, the patient remained reasonably healthy until his death two years later due to stroke associated with cerebral metastases.