The natural history and appropriate treatment of giant liver haemangioma remain poorly defined. The diagnostic strategy and the results of a longitudinal study of 78 such lesions are described. Sixteen resected patients and 62 with asymptomatic giant haemangiomas were entered into a follow-up programme consisting of clinical assessment and abdominal ultrasonography every 6 months. Resection was considered only for symptomatic patients (14 cases) and rapidly growing lesions (two cases). The mean follow-up was 36 months for the resected patients and 55 months for the observed group. Surgery permanently relieved symptoms. No recurrence of haemangioma was observed. Some 32 of 36 unresected lesions followed up remained stable in size. Minor changes were observed in four of 36. None ruptured or became symptomatic. It is concluded that asymptomatic large haemangiomas can be managed safely by observation. However, the occasional occurrence of rapid growth might represent a further indication for resection and justifies strict imaging follow-up. The pattern of growth, rather than absolute size, of a lesion is suggested for selection of asymptomatic patients who might benefit from preventive surgical excision. When feasible, the authors prefer enucleation to remove giant haemangiomas.