In order to establish a system for structural studies of the murine class I major histocompatibility antigen complex (MHC) H-2Kd, a bacterial expression system and in vitro refolding preparation of the complex of H-2Kd with human beta2m and the immunodominant peptide SYVNTNMGL from hepatitis B virus (HBV) core-protein residues 87-95 was employed. The complex (45 kDa) was crystallized; the crystals belong to space group P222(1), with unit-cell parameters a = 89.082, b = 110.398, c = 47.015 A, alpha = beta = gamma = 90 degrees. The crystals contain one complex per asymmetric unit and diffract X-rays to at least 2.06 A resolution. The structure has been solved by molecular replacement and is the first crystal structure of a peptide-H-2Kd complex.