Membership in the broad family of scavenger receptors has grown significantly. Two new scavenger receptor receptors have been cloned (SR-BI and SR-CI) and a previously isolated integral membrane protein (CD36) has been found to possess lipoprotein binding properties that entitle it to be included in the family. The breadth of ligand recognition of this class of receptors has also increased with the discovery that high-density lipoproteins and anionic phospholipids can bind to scavenger receptors. New studies linking these receptors to apoptotic and signal transduction pathways have further enlarged their potential contributions to normal immune function as well as the process of atherosclerosis. Clarifying the physiologic as well as pathophysiologic significance of these multifunctional proteins has proven challenging, but mouse homologous recombination technology will soon yield critical insights into the role scavenger receptors play in atherosclerosis and other macrophage-associated immune functions.