In the present report we describe patterns of traumatic events and Post-traumatic Stress Disorder (PTSD), both partial and full, among homeless youth and those at risk for homelessness, with an emphasis on gender differences. Participants were 85 homeless and at-risk youth (49% female) recruited from a drop-in center in New York City in 2000. Youth completed a structured interview lasting 1.5 h. Rates of childhood maltreatment were substantial. Further, almost all youth experienced at least one traumatic event, with most experiencing multiple types of trauma. Gender differences were found in the types, but not prevalence or magnitude, of childhood maltreatment and traumatic events experienced. Partial symptomatology of PTSD was common for females but not males. Symptoms of depression and anxiety were found to co-occur with PTSD for females, which may complicate treatment efforts. Further investigation of the impact of trauma on homeless males is needed.