Classical galactosemia is the most common disorder of galactose metabolism. Symptoms appear in the neonatal period after ingestion of galactose and include vomiting, diarrhea, failure to thrive, lethargy, hypotonia, jaundice, hepatomegaly, septicemia, cataracts and bleeding tendencies. If a galactose-restricted diet is initiated rapidly, the neonatal symptoms resolve and the complications of liver failure, sepsis, neonatal death and mental retardation can be prevented. Despite adequate galactose restriction from an early age children with galactosemia are at risk for ataxia, verbal apraxia, delayed speech and developmental delay. Females with galactosemia are at risk for premature ovarian failure.