The author outlines & discusses what he & colleagues have recognized as 5 major challenges in suicide prevention: 1) an inability to discriminate the relatively few true cases from large numbers of false-positive cases; 2) the large number of false-negative cases that escape preventive detection; 3) the inability of clinical & social services to reach many individuals who have suicidal intent; 4) a continuing paucity of knowledge about fundamental biological, psychological, social, & cultural factors that contribute to suicide risk among diverse populations & groups; & 5) the lack of coordinated strategies for suicide prevention that can deal effectively with myriad local, regional, state, & national agencies & organizations that could, in theory, play a role in preventing suicide. JA