The accuracy of the clinical diagnosis of 1292 non-melanotic skin tumours that were submitted to a private pathology service in 1980-1981 was determined. The clinical diagnosis that was written on the pathology slip which was submitted with the tumour was correlated with the histological diagnosis and the type of medical practitioner submitting the lesion. The clinical diagnosis was most accurate in the case of basal cell carcinoma; dermatologists most often reached this diagnosis correctly. For squamous cell carcinoma, although most frequently the lesions were diagnosed correctly clinically by dermatologists, their clinical diagnosis was confirmed in only 51% of cases. On average, 36% of squamous cell carcinomas were diagnosed clinically as basal cell carcinomas. The clinical course of 299 patients with a total of 305 squamous cell carcinomas that were selected from the squamous cell carcinomas that were submitted in 1980-1981 was traced. Four tumours (1.6%) which occurred in sun-exposed areas of the body metastasized, and 18 (7.5%) recurred locally. We conclude that those non-melanotic skin tumours which have the most potential to metastasize (squamous cell carcinomas) are those which are most poorly diagnosed clinically. It is recommended that patients with non-melanotic skin cancers should undergo biopsy as a routine to confirm the clinical diagnosis. Those who have a squamous cell carcinoma removed should be followed up for at least two years after the initial treatment.