AbstractSibling correlations were evaluated and segregation analysis was performed on age‐dependent maculopathy scores of the right and left eyes of individuals from 564 families in the Beaver Dam Eye study. There is evidence of significant sibling correlations. The data fit a mixture of two normal distributions, especially after undergoing the Box and Cox power transformation. In each eye, the hypothesis of mendelian transmission of a major effect cannot be rejected under the τ'ABfree model, but is rejected under the τ's free model. The hypothesis of a random environmental major effect is rejected. Similar major gene parameter estimates are found for both eyes. The results are consistent with a major effect accounting for 62% and 59%, in the right and left eyes, respectively, of the determination of age‐related maculopathy scores. A single major gene can account for about 89% and 97% of this variability due to a major effect, or for about 55% and 57% of the total variability, in the right and left eyes, respectively. © 1994 Wiley‐L