Three studies examined the diagnosis of posttraumatic stress disorder (PTSD) in agencies treating at risk youth. Studies 1 and 2 (1999) found that baseline PTSD diagnosis was rare in a residential and an outpatient agency (2.3% and 5.4%, respectively) whereas trauma-focused interviews identified PTSD in 47.7% and 44.6% of these clients. Subsequent training efforts increased awareness of PTSD and recognition of unique issues in assessing at risk youth. Study 3 (2009) reexamined PTSD diagnosis rates in these agencies 10 years later and found that the residential agency had an increased rate of PTSD diagnosis (10.8%), whereas PTSD diagnosis remained rare in the outpatient agency (4.0%). Suggestions are offered for increased accuracy in the diagnosis of PTSD and complex PTSD with at risk youth.