There are three separate disorders of galactose metabolism of clinical importance. Galactokinase deficiency mainly causes cataracts which regress without complications providing a galactose-free diet is started early enough. UDPgalactose-4-epimerase deficiency seems extremely rare. A common feature of the two reported cases is nerve deafness. Galactose-1-phosphate uridyl transferase deficiency poses the greatest problems because of the poor long-term outcome in spite of a galactose-restricted diet, and with no clear indications of how and when the underlying damage occurs. Recent evidence of low erythrocyte and tissue UDPgal levels, associated with ovarian dysfunction, may indicate impaired galactoside synthesis. Administration of uridine corrects the UDPgal depletion and trials in which it is added to the galactose-restricted diet have begun.