Several studies have suggested that suicidal behavior is at least partially determined by genetic factors, supporting a search for related genes. Two genes that have been highlighted in the literature as being involved are HTR1B, which codes for the serotonin 1B receptor, and COMT, which is related to the inactivation of catecholamines. In order to assess the combined evidence for the numerous studies that have been published relating suicidal behavior to these two genes, two different random effects meta-analyses were conducted utilizing seven studies related to HTR1B and six studies related to COMT. For HTR1B, the combined evidence from 789 case and 1,247 control subjects/participants, suggested that there was no significant association between the HTR1B G861C polymorphism and suicidal behavior. For COMT, based on the combined data from 519 cases and 933 control subjects, there was evidence of a significant association between the COMT 158Met polymorphism and suicidal behavior. Although the results for COMT were not influenced by publication bias, the significance of the combined results was not robust and was related to the gender of the case and control subjects. The results for COMT support past literature that has found a relationship between suicidal behavior and COMT, and has also found that the relationship differs for males and females. Given that in the United States a higher proportion of females attempt suicide, and the higher proportion of males successfully commit suicide, it is possible that COMT is related to the lethality of suicide attempts. © 2007 Wiley-Liss, Inc.