All 3 children, 2 boys and 1 girl (the probands), in a family had high myopia and subnormal visual acuities. The boys had high myopia in both eyes, the girl had high myopia in 1 eye and low myopia in the other eye. Both of the boys had a protanomalous colour vision defect. The colour vision testing of the high myopic eye of the girl was not successful, the other eye had normal colour vision. In the electroretinogram examination, both cone and rod responses were decreased in 2 of the children. In the family study, results of an eye examination of 30 relatives were available. No other cases of high myopia or subnormal visual acuities were found. The father of the children, 1 of the paternal relatives, and 5 of the maternal relatives had low myopia. One maternal male cousin of the probands had a protanomalous colour vision defect. In the genealogical study, no relationship was found between the families of the father and the mother of the probands going back to the fifth generation. The heredity of this disorder is difficult to define. It could be autosomal dominant or recessive if the myopia only are taken into consideration. If the high myopias and cone dysfunction are considered to be parts of the same syndrome, the heredity could be x-chromosomal recessive or autosomal recessive.