O June8-10,1981, the Lipid Metabolism-Atherogenesis Branch of the National Heart, Lung, and Blood Institute sponsored a workshop entitled, "The Relationship of Hypertriglyceridemia to Atherosclerosis," in Bethesda, Maryland. The purpose of the workshop was to bring together a large number of investigators with primary interests in epidemiology, genetics, nutrition, pathology, and basic and clinical research to discuss recent advances in the knowledge of triglyceride metabolism and to summarize the relationships of the hypertriglyceridemias to atherosclerosis. The agenda was planned by Drs. Elizabeth Barrett-Connor, Bryan Brewer, John Brunzell, Christopher Fielding, Scott Grundy, Kenneth Lippel, Arno Motulsky, and Donald Zilversmit. More than 80 scientists attended the workshop; 26 made formal presentations or served as panel discussants. The other attendees participated in the discussions and in the question and answer periods that followed each presentation. We present here a summary of the major presentations made at the workshop as well as a list of some questions that will likely be the basis for future research in triglyceride metabolism and in the relationships of the hypertriglyceridemias to atherosclerosis. The summary is organized into three sections which correspond to the framework of the workshop.