In order to obtain an experimental model for studying inherited disorders of galactose metabolism in man, we administered to adult rats a diet supplemented with 50% of galactose during 38 days. The results showed clinical symptoms such as polyuria, polydipsia, growth retardation and bilateral cataract. The main biochemical features were an increase in the galactokinase and uridyltransferase activities in liver, an ubiquitous accumulation in tissues and a considerable urinary elimination of galactose and galactitol, a weak accumulation of galactose-1-phosphate in tissue and a hyperaminoaciduria. This work led us to quantify the respective importance of the major pathway and minor pathways of galactose in the rat after a galactose-rich diet.