This prospective study of suicidal emergency department (ED) patients (ages 10–18) examined the timing, cumulative probability, and predictors of suicide attempts through 18 months of follow-up. The cumulative probability of attempts was as follows: .15 at 6 months, .22 at 1 year, and .24 by 18 months. One attempt was fatal, yielding a death rate of .006. Significant predictors of suicide attempt risk included a suicide attempt at ED presentation (vs. suicidal ideation only), nonsuicidal self-injurious behavior, and low levels of delinquent symptoms. Results underscore the importance of both prior suicide attempts and nonsuicidal self-harm as risk indicators for future and potentially lethal suicide attempts.