Although there are numerous publications on the existing link between month of birth and suicide, only two studies focus on suicide attempts and auto-aggressive behavior. Research data suggest that month of birth is related to a variation of 5-HIAA in the cerebrospinal fluid, which correlates with violent behavior (VB). Therefore, the aim of this study is to search, for the first time, for a possible link between month of birth and the occurrence of VB in emergency, for patients admitted for a suicide attempt with medication. This is a 10 months prospective study among all the patients of the canton of Geneva, Switzerland, admitted in emergency for a suicide attempt with medication. During a 10 months study period we included 493 patients, of which 77 (15.62%) presented VB. Higher incidence of VB was found in subjects where born at the end of winter and the beginning of spring, with a maximum for April and a minimum for December. In spite of a relatively small number of subjects, it seems promising to study the occurrence of VB as a function of month of birth in patients admitted in emergency for a suicide attempt.