The authors report the case of a malignant haemangiopericytoma found in an uncommon location, namely the mesorectum. Haemangiopericytomas of the mesorectum are rare mesenchymal tumours of vascular origin that usually occur in the musculature of the extremities, retroperitoneum, pelvis (uterus, ovary and urinary bladder), head, neck and lungs. Rare sites include the liver, pancreas, stomach and greater omentum. Because of their rarity the overall experience has not been significant and little has been published concerning such tumours. In addition, the difficult interpretation of the histological evidence and the poor prognosis of the disease may still give rise to problems in terms of clinical management. Haemangiopericytomas of the retrorectal space, however, seem to behave like malignant tumours: the clinical course is poor and survival short, despite radical surgery, due to early distant metastases and local recurrence. Surgery still remains the mainstay of treatment. Adjuvant therapies should be considered.