Although some studies have been carried out about suicidal behavior in the adolescence in Colombia, it has been necessary to carry out research with larger samples and from different regions of the country, examining aspects of ideation such as suicidal planning, which tends to predict suicidal attempts, taking into account that sex differences in attempts and such ideation among Colombian adolescents have not been sufficiently investigated. This study examined sex differences in the number of suicide attempts and suicidal ideation (seriously thinking about suicide and planning to commit suicide in the last twelve months), among 1659 adolescents aged 13 to 19 years (54 % female), from four cities of Colombia (Bogotá, Bucaramanga, Tunja and Yopal). In addition, adolescents who reported having thought of a suicide plan were compared with those who had not, in a series of individual and socio-family variables previously related to suicidal behavior. The instruments used were the Checklist SCL-90-R, the Conflict in Adolescent Dating Relationships Inventory (CADRI), the Behavior Assessment System for Children 3rd Ed. (BASC-S3), a self-report questionnaire on psychological variables, and a self-report questionnaire on incidents of violence between parents witnessed by adolescents. Non-parametric tests (Mann Whitney U, effect size for this test, Chi Square, Odds Ratio) were used, due to the nominal and ordinal nature of some variables and because the quantitative variables were not normally distributed in the sample. Women reported more suicide attempts than men, and significantly more (p = .05) reported serious thoughts of suicide and a suicide plan. The participants who thought about a suicide plan in the last twelve months presented a significantly higher range of scores (p = .05) of the psychopathological symptoms measured with the SCL-90R and the BASC-S3, such as somatization, obsessions-compulsions, depression, anxiety, hostility and psychoticism, in the global severity index of the SCL-90R, in the clinical and school maladjustment indices of the BASC-S3, as well as a smaller range of scores in the personal adjustment index and the scales of this BASC index (interpersonal relations, relations with parents, self-esteem and self-confidence). They also reported a higher frequency of sexual, relational, verbal-emotional, physical violence and threats from their partner or ex-partner, examined by the CADRI, as well as a higher consumption of alcoholic beverages, marijuana and inhalants, violent physical punishment by parents or another caregiver, feeling neglected by the father and mother, running away from home, poor relationships with parents and siblings, and poor academic performance. The probability of thinking about a suicidal plan was higher (OR = 2.0) among those who reported feeling so sad or hopeless that they had to interrupt their normal activities, almost every day, for two weeks or more; having been physically punished in a violent way by a parent or other caregiver; having been forced to a sexual act by an older person, a peer, a family member or a stranger; having been abandoned totally or for a considerable time by the mother; having been thrown out of the house by one of the parents and having witnessed acts of physical, verbal or other types of violence between the parents. These results indicate that adolescents who have a greater vulnerability to suicidal behavior could be identified among those who present negative family circumstances, such as poor relationships with parents, domestic violence and observation of violence between parents, as well as negative social circumstances, such as poor interpersonal relationships, sexual violence and intimate partner violence, which could lead to the development of psychopathological symptoms, substance use, poor academic performance and other manifestations of clinical, educational and personal maladjustment, in order to carry out an intervention that decreases the likelihood of suicide attempts. They also show the importance of developing prevention alternatives from an ecological perspective, including peers, parents and teachers. [ABSTRACT FROM AUTHOR]