Among the first 52 recipients of primary liver allografts with follow-up of 2 weeks or greater, 6 patients had biopsy-confirmed vanishing bile duct syndrome (VBDS) and required retransplantation. Five of these six patients had positive lymphocyte crossmatches. Of the 46 remaining liver transplant recipients, 11 had positive crossmatches. Thus, the incidence of VBDS was 5/16 in recipients with a positive crossmatch and 1/36 in recipients with a negative crossmatch. The positive-crossmatch group was significantly more likely to develop VBDS than the negative-crossmatch group (P less than 0.004, log rank test). Additional HLA studies comparing degree of donor-recipient mismatch at the various HLA loci showed no significant difference between the groups for class I disparity. However, class II mismatch was of borderline significance (P less than 0.056). When evaluated individually, the DQ mismatch (P less than 0.04) appeared to be more important than the DR mismatch (P = NS). Our data suggest that a positive lymphocyte crossmatch and a class II mismatch, in particular HLA DQ disparity, may play an important role in the pathogenesis of VBDS.