Major advances have been made in our understanding of the phenomenology and course of grief in adults. However, little is known about the course of grief in children and adolescents.We report on the course of children's and adolescents' grief reactions after sudden parental death and the effect of those reactions on subsequent psychiatric and functional status.Longitudinal study (July 1, 2002, through January 16, 2007) of bereaved children, adolescents, and families, with yearly comprehensive assessments as long as 3 years after parental death.Bereaved children and adolescents and their surviving parents recruited through coroners' records and a newspaper advertisement.A total of 182 parentally bereaved children and adolescents aged 7 through 18 years whose parent died due to suicide, unintentional injury, or sudden natural causes.Grief, functional impairment, and incident depression.Three distinct trajectories of grief reactions were observed in the study participants. In 1 group, which consisted of 10.4% of the sample, grief reactions showed no change 33 months after death. Children and adolescents with prolonged grief reactions had higher rates of previous personal history of depression. Prolonged grief made unique contributions to increased levels of functional impairment, even after controlling for the clinical characteristics before and after the death. Conversely, prolonged grief in children, adolescents, and the surviving caregiver predisposed children and adolescents to an increased hazard of incident depression. Another group (30.8%) showed increased grief reactions 9 months after the death, which gradually decreased over time. Despite this finding, grief reactions in this group also were associated with functional impairment and increased risk of incident depression.Grief reactions abate over time for most children and adolescents bereaved by sudden parental death; however, a subset shows increased or prolonged grief reactions, which in turn increases the risk of functional impairment and depression. Research regarding interventions designed to relieve the burden of grief in bereaved children and adolescents are needed. Such efforts also should assess and address grief reactions in the surviving parent.