In spite of adequate dietary regimen, many patients with galactosemia have developmental abnormalities. We studied 8 patients with galactosemia, aged 9 months to 19 years who had all been treated with a galactose-free diet from an early stage. Neurological functioning, general developmental, and language and speech development were assessed in all cases. The results show that even medically well treated children and young adults with galactosemia are at risk to develop disabilities, including mental retardation, speech and language disabilities. Verbal dyspraxia was diagnosed in 3 of 6 patients, who had acquired verbal language, all with IQ 70 or below. This may indicate that verbal dyspraxia is just one symptom among others in patients with galactosemia and mental retardation.