Recent experiments from our laboratory, as well as those of several other investigators, have focused upon the identification and characterization of specific membrane-localized receptors for bacterial endotoxic lipopolysaccharides on mammalian cells. In this article, we have summarize the results of these studies with a primary emphasis upon experiments from our own laboratory. It would appear that some differences between laboratories in the identification of LPS receptor may be the result of different experimental techniques employed. In spite of these differences, however, there is an emerging picture which defines several LPS binding proteins as potentially dominant candidates for the functional LPS receptor on the cell membrane, including a protein of 70-80 kDa and perhaps a second protein of 30-40 kDa as well. Other membrane proteins with important functions in the cellular response to LPS include CD14, the CD11/18 family of adhesins and the 95 kDa scavenger receptor. Identification of specific cell membrane targets for LPS has important implications for immunotherapy of septic shock and perhaps cancer as well.