In a material of 839 Greenland Eskimos with no corneal abnormalities, the variations of central corneal thickness (CT) were analysed from a genetic point of view. Environmental factors were suggested by a town-village difference in mean CT level (excess in town), by a higher CT level in families with an indoor occupation, and by a nearly significant husband-wife CT correlation. Using an age-sex-location-independent CT deviation score (CTDS) the family variations were studied in 86 families with two parents and one to seven children, and in 187 sibships with two to seven sibs. The first degree relationships showed a fairly high level of resemblance, which seems to indicate a major genetic influence on CT, with heritability estimates about 0.6--0.7. In men an association was found between CT and Caucasian admixture, which also suggested genetic factors. However, both findings call for reservation because of the socioeconomic environmental influence.