Suicide now ranks among the leading causes of death in the United States and Canada. Furthermore, in the States the homicide rate has become a matter of concern (5, 6). The increasing incidence of these problems has preoccupied many researchers and considerable efforts have been made to identify et1ologlc31 factors. Virtually no stone has been left unturned. Variables studied ranged from birthdays ( I ) , death anniversary reactions (2), and moon phases (3), to gross national product per capita and the proportion of females in the labor force (4). Recently Pellegrini (7) suggested yet another variable lor consideration. His biogenic hypothesis states that a predisposition to suicidal and homicidal behavior may have been induced in individuals who during their early development have been exposed to toxic radiation fallout from above ground detonation of nuclear weapons. The author does not provide empitical data in support of the hypothesis but proposes that toxic radiation is a factor worthy of consideration in multivariate analytic inquiry into the complex epidemiology of violent death. Although i t is an interesting proposition, I fear that the researcher who accepts the challenge of inves~igating this hypothesis will encounter considerable difficulties. First, there will be the methodological problem of identifying and assessing the population under consideration. Second, assuming that one regards the effect of radiation as a biological correlate, the heterogeneity of the target populations and the overlap of the violent behaviors and illnesses such as depression will make it difficult to obtain significant and replicable correlations between the behaviors in question and the possible biological factor(s). Third, risk factors with a low or moderate specificity such as toxic radiation, when applied to events with low base rates such as suicide and homicide, will inevitably result in high numbers of 'false positives.' Finally, it appears that exposure to toxic radiation is merely a proxy variable for more fundamental processes, processes that are already subject to investigations by other researchers. I suggest that more d i r e c ~ evaluations of neurochemical, biochemical, genetic, and social-psychological factors as part of a multidimensional approach to the causal explanation of suicide and homicide will lead to more fruitful results.