There is recent, although limited, evidence that among men the risk of death from suicide is strongly inversely related to body weight. An unanswered question is whether the reported association between relative body weight and suicide holds for men and women equally. This study aimed to determine the effects of body mass index on suicide risk among men and women in the United States. We analyzed data from the combined 1986-1994 National Health Interview Surveys linked to the 1986-2002 Multiple Cause of Death file through the National Death Index. Survival analysis indicated that for each 5 kg/m2 increase in body mass index the risk of suicide decreased by 18% and 24%, for men and women, respectively. These findings may help us to better understand and prevent suicide. However, further research is needed to unpack the observed association between body weight and suicide risk into its component pathways and mechanisms.