The purpose of this study was to examine the evidence to determine if there are gender differences in suicidal ideation of adolescents. This study examined the main effect of risk factors from 5 domains and protective factors from 1 domain in relation to suicidal ideation by gender and identified the most important predictors of suicidal ideation for males (N = 654) and females (N = 658). This study was a cross-sectional survey, and data were collected through self-report questionnaires. In the univariate analysis, especially, risk factors from behavioral variables and psychosocial-environmental variables appeared to be gender skewed. For males, all behavioral variables were predictive of suicidal ideation. For the females, unlike the males, "Wang-tta" or victim of bullying behavior and sexual orientation as behavioral variables were predictive of suicidal ideation. For males, parental divorce and parental alcohol abuse as psychosocial-environmental variables were predictive of suicidal ideation. For the females, again unlike for the males, all the psychosocial-environmental variables were not predictive of suicidal ideation. The most important predictors of suicidal ideation for males as a result of the multivariate analysis were history of suicidal attempt, depression, hostility, smoking, parental alcohol abuse, communication with friends, and self-esteem. The most important predictors of suicidal ideation for females as a result of the multivariate analysis were depression, hostility, sexual orientation, and self-esteem. These results would indicate that an effective suicide screening and prevention program for adolescents should consider gender differences.