Although a growing body of research has increased knowledge of the after-effects of trauma in children, including the development of PTSD, there are significant gaps in this knowledge concerning diagnosis, assessment, and associated features. With regard to diagnosis, variations in symptomatic expression of PTSD in children have been proposed; however, there have been few examinations of the validity of these variations in terms of course and consequence of PTSD defined in these ways. Several factors increase children's risk for development of PTSD or PTSD symptoms after trauma. Such information is potentially useful for identifying children who may benefit from more thorough or ongoing assessment after trauma. With regard to assessment, an array of increasingly sophisticated and clinically useful measures is being developed; however, currently there is a dearth of high quality data concerning the diagnostic use of different assessments. An area of general weakness concerning these assessments is the limited data on discriminant validity. A sizeable body of evidence indicates that trauma can produce diverse reactions in children, including a general increase in internalizing and externalizing symptoms. Clinically useful measures allow PTSD to be differentiated from this general reaction to traumatic events, much of which may reflect a nonpathologic response. With regard to associated features, limited information suggests that PTSD can have a cascading negative effect on children's development and functioning. More research is needed, however, to delineate factors that reflect risk for PTSD after trauma, factors that reflect consequences of PTSD, and mediating variables.