Data in this report demonstrate a linkage between glucocorticoid-induced cleft palate susceptibility and H-2. B10.A × C57BL/10F1 females were backcrossed to C57BL/10 males. Cleft palate was induced in the BC1 fetuses by giving pregnant females 80 mg/kg of dexamethasone intraperitoneally (IP) on day 12 of gestation. The H-2a/b haplotype was detected on day 18 BC1 fetal spleen cells with an indirect immunofluorescent labeling technique. Fetuses without antigen H-2Kk were H-2b/b. H-2a/b fetuses had a cleft palate frequency of 29%; 11% of the H-2b/b fetuses had cleft palate (P < .01), demonstrating that the higher suceptibility to cleft palate segregates with the H-2a haplotype.