There were 16 cases of orbital recurrence in a consecutive series of 317 children with retinoblastoma referred to a specialist centre. The incidence of orbital relapse amongst children treated at the centre from the outset of their disease was 2.5%. In every case the patient was the first affected family member. The ocular tumour was therefore not anticipated and had commonly been detected at an advanced stage. Systemic staging investigations detected extraorbital spread in six of the 16 and none of these children survived. One of the remaining ten children with no evidence of dissemination at the time of diagnosis of orbital recurrence is a long-term survivor. No child survived after orbital exenteration or radical orbital radiotherapy alone. Three children received a combination of radiotherapy and adjuvant chemotherapy. Only one of the three was free from systemic disease at relapse and this child is the only survivor. In children apparently free from widespread retinoblastoma at diagnosis of orbital recurrence, distant relapse was the commonest cause of death though several children died from direct intracranial extension. It is advocated that orbital recurrence of retinoblastoma is treated by excision biopsy of the tumour mass followed by radical orbital radiotherapy to a dose of 50 Gy. This should be combined with adjuvant chemotherapy and, where a risk of direct intracranial extension exists, by neuraxis irradiation. No other child in this series with evidence of local extraocular extension of retinoblastoma at enucleation and who had received radical orbital radiotherapy to a full dose of 50 Gy subsequently recurred in the orbit.(ABSTRACT TRUNCATED AT 250 WORDS)