This volume is a collection of the lectures and commu- nications presented at the Nato Advanced Study Institute on "Liver, Nutrition and Bile Acids" held in Maratea, Italy, September 1983. The research areas covered by the Meeting are very wide, having to do with the liver and biliary pathophysiology, nutrition, gallstone disease and atherosclerosis prevention. Scientists from the major clinical and basic disciplines provided an update overview of the complex mechanisms regula- ting the biosynthesis and catabolism of cholesterol and the formation and metabolism of bile acids. The NATO ASI has given the opportunity for thorough general discussions on problems of growing interest in medical sciences in the spirit of the NATO Meetings. This wealth of information is reflected in the present collection. We are grateful to all the contributors for the pre- sentation of the results of their research. A particular thanks is addressed to Mrs. Brita Rolander Chilo of the Nutrition Foundation of Italy for her invaluable advice and for the organization of the Institute as well as for the editorial work. Giovanni Gall,i Enrica Bosisio v CONTENTS Coordinate Regulation of the Three Enzymes in Cholesterol Biosynthesis * ****** 1 Ajit Sanghvi Microsomal Cholesterol 7a-Hydroxylase Phosphatases.