133 patients with congenital or idiopathic cataracts were studied (94 patients had ages between 1 month and 14 years; 10 patients had ages between 16 and 50 years and 29 patients did not have an age registry) along with 18 patients with a clinical diagnosis of classic galactosemia. The activity of galactokinase (GALAK) and that of erythrocyte galactose-1-phosphate uridyl transferase (GALT) was measured. There were no individuals with a total deficiency of GALK or GALT. The cataract patients of ages between 1 monthly and 14 years, 3 (3.19%) and 4 (4.25%) showed GALK and GALT levels in the range corresponding to the respective heterozygotes. As compared with the expected incidence of heterozygotes in the general population (0.2% for GALK and 0.8% for GALT) we found a significant rise of individuals with low levels of enzymes for the metabolism of galactose. The possibility that heterozygote galactosemic states contribute a risk factor in the development of cataracts and its therapeutic implications are discussed.