The purpose of this study was to examine the rates of posttraumatic stress disorder (PTSD) among a sample of severely maltreated children and their mothers, and to investigate the age of onset of documented maltreatment in these children. The sample consisted of 109 pairs of women and their children who were before a juvenile/family court due to maltreatment of sufficient severity to warrant removal of the child from parental custody. Children were examined using the PTSD Section of the Diagnostic Interview for Children and Adolescents, Revised 6th Version (DICA-6-R). The PTSD Module of the Structured Clinical Interview for DSM-III-R (SCID) was administered to all mothers. Clinical psychiatric interviews were also administered to all children and mothers. From the sample of 109 cases, 15.6% of the mothers met SCID criteria for a current presentation of PTSD, while 36.7% had a past history of PTSD. Of the 109 evaluated children, 35.8% met current DICA criteria for PTSD. Posttraumatic stress disorder is significantly overrepresented in the children of mothers diagnosed with PTSD (p = .001). The average age of maltreatment onset was 46.4 months among the children diagnosed as PTSD, and was 61.3 months in the group of seriously maltreated children who did not develop PTSD (p = .038). The onset of maltreatment is significantly earlier among children whose mothers meet PTSD criteria than among other maltreated children (p = .025). Intergenerational transmission of violence and developmental effects of traumatic experiences upon the young child are discussed.