This study examined the chronicity of PTSD in 530 male and female Vietnam veterans who were drawn from 2 large, ethnically diverse samples. Delayed onset was common, as was a failure to fully remit: 78% of the 239 veterans with full or partial lifetime PTSD were symptomatic in the 3 months prior to assessment. Cluster analysis identified 4 subtypes of posttraumatic response, with women most likely to be in a delayed onset cluster, and minority men most likely to be in a severe chronic cluster. The extent of chronicity observed in this sample underscores the need for treatments that address the persistence of posttraumatic symptoms.