To study the possible association between diet and gallstones we investigated these two variables in two populations in Tel Aviv and Gaza with presumed differences in both. Gallstones were more frequent in Jews in Tel Aviv than in Arabs in Gaza, 12.1% versus 3.8% (p less than 0.001). This difference was fully accounted for by the 60+ age groups in both populations. There were no significant differences in the frequency of gallstones among the 20-39 and 40-59 age groups. Numerous and marked differences in diet composition were found between both populations. Energy, carbohydrate and fiber intake was higher in Gaza. The consumption of unsaturated fats was greater in Gazans and their P/S ratio was higher, 0.92 versus 0.70 in Tel Aviv. Beef and fish were usually eaten in Gaza while poultry was more frequently consumed in Tel Aviv. There were also differences in vitamin and mineral consumption. It cannot be determined which, if any, of these dietary differences is related to the lower frequency of gallstones in the older population of Gaza. Alternatively it could be the diet eaten in Gaza many decades ago, presumably poorer in protein and fat, which is responsible for these differences.