A retrospective analysis was undertaken of 120 patients with retroperitoneal sarcoma referred to the Royal Marsden Hospital over a period of 20 years. The actuarial 5-year survival rate of all cases following referral was 29 per cent. On univariate and multivariate analysis the principal factors associated with an unfavourable prognosis were the presence of metastases, poor performance status at presentation, high tumour grade and incomplete excision of the primary tumour. The single most important factor affecting the ability to remove the primary tumour completely was multiple organ involvement. After apparently complete excision, however, the probability of local recurrence by 5 years was 85 per cent (95 per cent confidence interval 56-99). The prognosis of patients with retroperitoneal sarcoma is poor.