Amphipathic a helixes and amphipathic β sheets are important surface lipid-associating motifs in plasma lipoproteins and membrane proteins. Amphipathic α helixes provide readily reversible lipid association, act as peptide detergents, and have optimal interactions with phospholipid bilayers. Amphipathic β sheets, on the other hand, interact with lipids in an essentially irreversible manner, completely lack detergent properties, and, in plasma lipoproteins, are likely to interact more readily with phospholipid monolayer:neutral core lipid emulsion particles than with phospholipid bilayers. Peptide mimics of these two surface-associating motifs have proven useful in establishing both the physical chemical and the biological properties of these motifs as analogues for the intact surface-associating proteins of which they are an integral part. To further aid in our understanding of these motifs, computational methods for simulations of interactions of these motifs with lipid surfaces have been developed and are undergoing refinement. © 2002.