A five-day-old boy was referred with a soft-tissue mass in his right upper arm. Plain radiographs and ultrasound demonstrated a lesion extending from the axilla to the elbow on the posterolateral aspect of the humerus. Open biopsy confirmed the diagnosis of congenital haemangiopericytoma. After MRI and selective angiography, excision biopsy was carried out, but no adjuvant therapy was administered. At further examination, four years and ten months later, he was noted to have three small nodules at the site of the original tumour. Excision biopsy confirmed this to be a local recurrence, although the lesion was less cellular with no appreciable mitotic activity. Congenital haemangiopericytoma is a rare cause of a soft-tissue mass in children. Most tumours are benign, and recurrence is uncommon. The treatment is controversial, but most centres recommend the use of adjuvant chemotherapy, combined with complete excision. We recommend treatment with doxorubicin. Orthopaedic surgeons should be familiar with this tumour since 30% to 50% of cases occur in the limbs