Seven cases of the infantile form of Huntington's disease--six boys and one girl--were observed in the space of six years. Six children showed the hypokinetic-rigid form of the disease. Results of clinical, speech evaluations, laboratory tests, EEG and LPEG corresponded with data in literature. Initial signs and symptoms were mild sensorimotor and behavioural disturbances. In five patients, all affected by the hypokinetic-rigid form, CSF HVA and 5HIAA were determined. CSF HVA levels were found to be significantly lowered in three patients. One child showed significant decrease of CSF 5HIAA. Levodopa, orally administrated to these five patients during 8 days to 6 weeks in dosages of 75 to 600 mg per day, induced in all a marked improvement of the hypokinesia and/or rigidity, speech and social behaviour. Two children developed slight choreatic movements and one child had to be withdrawn from the drug because of decrease of appetite.