A prospective study of the prevalence of gall stone disease at necropsy in a stable population has been undertaken over a 10 year period up to June 1988. In women, the prevalence of gall stone disease remained static but in men aged 50-59 years it rose from 7% (n = 148) in the first three years to 18% (n = 138) in the last three years (p less than 0.01) and in men aged 60-69 it rose from 12% (n = 370) to 20% (n = 366, p less than 0.01). In the latter age group the female: male ratio fell from 2:1 to 0.8:1. The proportion of deaths from coronary heart disease in men fell slightly in those over 70 during the study period. There was a fall in deaths from coronary heart disease in all age groups in women. Men with gall stones were less likely to have had a cholecystectomy than women, and overall 88% of gall stones remained in situ. In a parallel clinical study, the number of cholecystectomies carried out in the same district fell by 18% over the 10 years without any apparent change in the provision of resources. Cholecystectomy remained almost three times more frequent in women. National data indicate that there have been major changes in the average diet before and during the period of study in favour of reducing coronary heart disease. There has been no change in mortality from coronary heart disease in young men but if the observed increase in the prevalence of gall stones in men and the decrease in deaths from coronary heart disease in women are real phenomena, it seems likely that they are diet related.