Congenital eye malformations were studied in a small geographical area in 212,479 consecutive births. For each of the 145 new cases studied during the period 1979 to 1994, more than 50 factors were compared in probands and in controls. The prevalence rate of congenital eye malformations was 6.8 per 10,000 for microphthalmia 1.7, anophthalmia 0.23, cataract 2.7 and coloboma 1.4 respectively. Sex ratio was 0.82. Prenatal diagnosis was performed in 18 cases and 7 cases were induced abortions. The more common types of associated malformations in the 81 affected cases (53.8%) with at least one anomaly other than an eye malformation were clubfeet, microcephaly, hydrocephaly, cleft lip/palate and facial dysmorphia. At birth infants with eye malformations and other malformations were smaller, weighted less and their head circumference was lower than in controls. Placental weight was also lower than in controls. Pregnancies with eye malformations were more often complicated by threatened abortion, oligoamnios and polyhydramnios. Mothers of children with congenital eye malformations took more often drugs during pregnancy than mothers of controls. Fathers of children with congenital eye malformations were more often exposed to occupational hazards than fathers of controls. There was a significant association between eye malformations and consanguinity of parents. The recurrence risk for first degree relatives of probands was 8.9%. First degree relatives of probands had more than three times the prevalence of non-eye malformations than controls. These results are of relevance to genetic counseling.