We have investigated the clinical presentation, laxative use and histopathology of 38 patients with a histological diagnosis of melanosis coli and measured the colonic epithelial apoptosis in these cases. The presence of lipofuscin was confirmed in all cases. Fifteen of the cases had constipation, whilst eight had diarrhoea. Neither constipation nor diarrhoea was present in 13 cases and both were present, at different times, in two. Laxatives had been used in all those with constipation, in only one with diarrhoea and in none of the others. The mean apoptotic count was significantly increased in those with melanosis coli compared with the controls. In the majority of cases with constipation there was no other abnormality, whilst an additional diagnosis was present in the majority of the remainder. Colonic epithelial apoptosis was increased in melanosis coli and the majority of cases were not associated with laxative use. These results support the proposed role of apoptosis in melanosis coli, but indicate that melanosis coli is a non-specific marker of increased apoptosis with many possible causes, of which the use of laxatives is only one.