Chromosomes of a ewe lamb born with atresia ani vaginalis were examined after a 72-hour culture of peripheral whole blood. The 2n number of chromosomes was 54,XX, with no apparent deviation from normality. Pedigree analysis of the ewe lamb indicated that her sire and dam were only slightly related (Rsd = 0.59%); therefore, the amount of inbreeding of the lamb was small (Fx = 0.30%).