A case of early childhood Coats's disease in a ten-month-old boy is presented. The lactic dehydrogenase aqueous:serum ratio was very high (6:1). A ratio higher than 3:1 in Coats's disease or in any other eye infection has never been reported except in cases of retinoblastoma. Since retinoblastoma does not always show calcification in x-rays, it may be concluded that in certain cases it would be impossible to discriminate between Coats's disease and retinoblastoma (except in pathologic analysis) with any available diagnostic tools.