The histological features of 234 conjunctival biopsies from Africans in Malawi have been re-examined. The appearances of solar keratosis, pinguecula, and pterygium are presented as part of a continuous spectrum of the same pathological process and aetiology, which may lead to carcinomatous change. The results are discussed with regard to the specific geographical distribution of such lesions found by other workers, with particular emphasis on ultraviolet radiation as the main aetiological factor.