Suicidal ideation during adolescence is quite common. Longitudinal ideation patterns may predict adolescents at greatest risk of progressing to more serious suicidal behaviors. We enumerated suicidal ideation trajectory subgroups and estimated subgroup association with later suicidal plans and attempts using data collected across a 13-year period from 552 Caucasian adolescents. Three subgroups were found: non-ideators (no ideation), decreasers (ideation decreased), and increasers (ideation persisted or increased). Probability of planning a suicide was greatest among increasers (females: .54, males: 51, p < .01). Probability of attempting suicide was greatest among male decreasers (.36, p < .01) and female increasers (.25, p < .01).