Huntington's disease (HD) is characterized by the presence of hyperkinesias, but bradykinesia is also present in most patients. We studied the motor performance of 18 patients with genetically proven HD (age, 38.5 ± 10 y; clinical stage, 1.7 ± 1.7; (CAG) triplet length, 49.2 ± 6.8 triplets; all but three patients were free from neuroleptics) and compared with a control group (n = 18) and with a typical Parkinson's disease (PD) group (n = 20). Motor study included the four timed tests commonly used for PD : Pronation-supination (PS), finger dexterity (FD), movement between two points (MTP) and walking test (WT). Tests were done at 9 AM. The PD group was studied in “off” condition, with no medication given for 12 hours. The HD group was slower than the controls on all tasks (all tests significant,p< 0.01, Mann-Whitney U test) and even slower than PD group (for FD,p< 0.05). A significant correlation was found between each test and clinical stage (for PS, r = 0.84; for FD, r = 0.75; for MTP, r = 087, and for WT, r = 0.77, Pearson). Severe bradykinesia was present in HD, and motor impairment is related to clinical stage.