Neurons in the hypothalamic lateral tuberal nucleus (NTL) were counted in 16 Huntington's disease (HD) patients and 12 controls. The control range was 47,500-71,700. In the HD cases the number ranged from 2,800 to 40,600. The log-transformed counts of the HD patients correlated closely with age-at-death (r = 0.66, P less than 0.01) and age-at-onset (r = 0.78, P less than 0.001), but not with duration of disease, nor with the severity of the neostriatal changes. Because of its vulnerability to the effects of the HD gene and its simplicity, the NTL seems fit to study the characteristics of neuronal death in HD.