Cultured fibroblasts from 7 of 14 corneas showed loss of a sex chromosome in 20-100% of metaphase cells. An X chromosome was lost from female cells, a Y from male cells. Sex chromosome loss was more common in ophthalmologically abnormal corneas but did not show a strong correlation with donor age or with longer time in culture. Clones characterized by autosomal aneuploidy and aberrations were present in corneal cultures from seven donors. Their presence was not related to the incidence of sex chromosomal loss or prolonged culture time. Our results suggest that human corneal cells have a tendency toward loss of a sex chromosome and toward autosomal change, and that such cells form clones. It has yet to be determined if corneal cells undergo these cytogenetic changes and clone formation in vivo.