Suicide behavior in Huntington disease (HD) was assessed by examining the proportion of deaths attributed to suicide among 452 deceased individuals with HD and the number and pattern of attempted suicides among a total population of 831 HD patients from the National Huntington Disease Research Roster. It was found that 5.7% of deaths among affected persons resulted from suicide and 27.6% of patients attempted suicide at least once. Comparison of this group with the general population indicated that the proportion of deaths due to suicide among persons with HD is almost four times greater than the corresponding proportion for the U.S. Caucasian population. Age at onset of HD was not significantly different between HD suicide and non-suicide patients, although suicide occurred more frequently in the early to middle stages of the illness. The "success" rate among HD suicide attempters did not differ from the general population rates in several western European countries. The relatively high suicide and attempted suicide rates in HD indicate that thorough psychological testing of at-risk persons and extensive patient support systems must be integral components of a program to identify HD gene carriers using a genetic marker.