Gallstones have become increasingly prevalent in Saudi Arabia, where cholecystectomy is now one of the commonest major abdominal operations. 2854 people underwent cholecystectomy in the 14 hospitals of the country's Eastern Province in the years 1977 to 1986. During this period the overall frequency of cholecystectomy increased by 978%, a finding not explained by the 67% increase in population or the 87% increase in other operations. Simultaneously, the average daily individual consumption of total calories, fat, and sugar increased by 81%, 197%, and 164%, respectively, and consumption of high-fibre grain fell by 75%. This striking increase in the frequency of cholecystectomy, which presumably reflects the incidence of gallstones, cannot be explained by demographic changes and seems more closely linked to the concomitant changes in dietary habits.