The specificity of binding of solubilized, purified HLA-A, B molecules to solid-phase peptides has been examined using the assay described by Bouillet et al. [1989. Nature (Lon4 339:473.] 64 peptides derived from the sequences of viral antigens, HLAA, B, C heavy chains, and clathrin light chains were tested for binding to HLAA2.1, Aw68.1, Aw69, B44, and B5, molecules that differ by 5-17 residues of the peptide binding groove. 15 of the peptides, including those known to be T cell epitopes, gave significant binding. The pattern of peptide binding for each of the five HLA-A, B molecules was not significantly different. Binding was demonstrated to be a property of native 02m-associated HLAA, B molecules that preserved conformational antigenic determinants after binding to peptide. In comparison to our previous results from solution-based assays the proportion of HLAA, B molecules that can bind solid-phase peptides is very high. This accessibility of solid-phase peptides to the binding site of MHC molecules may be directly related to the observed absence of MHC specificity in the binding. © 1990, Rockefeller University Press., All rights reserved.