Rectal leiomyosarcoma is rare, often large and found in the distal third of the rectum. Most symptoms differ from those of an adenocarcinoma. Staging is difficult and should include tumour size, necrosis, cellularity, number of mitoses and anaplasia. Abdominoperineal excision (APE) remains the only effective treatment. A 66 year old asymptomatic female presented with painless rectal bleeding after a fall. Digital examination and proctoscopy revealed a mass on the posterior rectal wall. Pelvic ultrasonography, arteriography and CT-Scan showed a huge retro-rectal lesion. Following APE, histopathology confirmed a leiomyosarcoma. No adjuvant therapy was given; there is no recurrence 4 years later.