Switzerland has one of the highest rates of adolescent suicide in Europe, but the prevalence of suicidal thoughts and attempts is unknown. The objective of this paper is to assess the prevalence of suicidal ideation and behaviour among Swiss teenagers and to identify the factors associated with suicide attempts. A self-administered anonymous questionnaire was distributed to a representative sample of 9268 15- to 20-year-old adolescents attending school or college. Six items focused on suicidal ideation and conduct. Multivariate analyses were performed to identify the health variables associated with suicide attempts. About 55% of the adolescents had no suicidal concerns; 26% reported suicidal thoughts, 15% reported suicidal plans and 3% reported suicide attempts. Suicide attempters reported significantly more problems in four areas, namely health behaviour, life events, social relationships and mental health. In conclusion, many factors associated with suicide attempts represent detectable behaviours. Thus health professionals could use this knowledge to be more effective in suicide prevention among adolescents.