We have reviewed 30 reports of Merkel cell tumour and described a further five cases in order to establish a database and from this more clearly define the biology of this tumour, prognostic factors that govern outcome, and optimal management. After excision alone of the primary lesion, local recurrence occurred in 39 per cent of patients and regional failure occurred in 46 per cent. In contrast, in patients treated by excision plus prophylactic treatment (adjuvant node dissection and/or adjuvant radiation), local recurrence occurred in 26 per cent and regional failure in 22 per cent. Locoregional recurrence carried an ominous significance with 67 per cent of patients subsequently dying of the disease. For patients who either presented with regional disease or later developed regional disease, the best outcome (44 per cent survival with mean follow-up of 40 months) was obtained following treatment by therapeutic node dissection with or without radiation. In contrast, treatment of regional disease with radiation alone was associated with only a 20 per cent survival rate. Unfavourable prognostic factors included young age, lesions sited in the head and neck or trunk, male sex, and the presence of locoregional failure and/or systemic disease. We conclude that Merkel cell tumours behave in a similar manner to the aggressive variants of melanoma and that minimal treatment consists of wide surgical resection of the primary lesion (with a margin of 2.5-3 cm) coupled with resection and probably also radiation of regional disease if present. In addition, consideration should be given to prophylactic node dissection in node negative patients, especially in those patients with unfavourable prognostic factors.