Clinical and epidemiological experience has shown that some subjects, such as diabetics and cirrhotics, are particularly prone to cholelithiasis. The cause of this association was sought, with particular reference to the biliary lipid pattern, since this was considered as a pathogenetic factor in high-risk patients of this kind. It was found that diabetics, like subjects with biliary lithiasis, have a high biliary cholesterol saturation index; this was not the case in cirrhosis. This increase was apparently due both to a fall in bile acids and an increase in bile cholesterol. On the other hand, no significant difference was found between diabetics and controls as far as the pool of bile acids was concerned. No important differences in bile acid pattern were noted. Deoxycolate tended to increase in subjects with cholelithiasis and fall (along with lithocolate) in those with cirrhosis. These findings were, however, devoid of statistical significance. The high incidence of cholelithiasis in diabetics is physiopathologically confirmed by significant "lithogenic" changes in bule lipid composition, whereas the high incidence in cirrhosis is not open to this explanation and probably rests on a different pathogenetic basis. The importance of bile saturation is clear, however, together with its therapeutic and prophylatic implications (chenodeoxycholic acid). The possible influence of unknown factors cannot be ruled out.