Recent data suggests there may be genetic & biologic risk factors for suicide. This paper reviews studies from clinical populations, twins, the Amish, as well as data from the Iowa-500 & Danish-American adoption studies which suggest that there may be a genetic factor predisposing to suicide. This paper also reviews neurochemical data from cerebrospinal fluid, urine & postmortem studies which suggest that diminished central serotonin & dopamine may be implicated in suicidal behavior. (29 refs)