Thin malignant melanomas, i.e. tumours less than 1 mm, are generally considered to have a good prognosis. The records of 148 patients with thin invasive melanomas located to the head and neck region were reviewed. All patients were followed for the excision of the primary tumour until death, or the closing date of this study (31 December 1989). Follow-up was median 9.6 years, (range: 3 months to 26.5 years). Increasing tumour thickness led to an increasing number of recurrences. However, there was no statistically significant difference in the length of recurrence-free survival or total survival between patients with tumours less than 0.76 mm and patients with tumours measuring between 0.76 mm and 0.99 mm (P>0.08). Tumours located in the scalp, neck and ears did relapse more often than tumours located to the face (P or = 2.0 cm (P>0.29). Sixteen of the patients (11%) developed recurrences, 12 of these 16 patients (75%) died of disseminated melanoma. We conclude that thin head and neck melanomas do not necessarily carry an excellent prognosis. Prognosis is not dependent upon tumour thickness when less than 1.00 mm.