Seven participants who did not meet the Diagnostic and Statistical Manual of Mental Disorders (3rd ed., rev.; American Psychiatric Association, 1987) criteria for posttraumatic stress disorder (PTSD) 1-4 months post- motor vehicle accident (MVA) and developed delayed onset PTSD during a 1-year follow-up interval were compared with 38 MVA controls who did not develop PTSD, as well as to 62 MVA participants who met criteria for acute onset PTSD on variables related to demographics, pre-MVA functioning, post-MVA functioning, and follow-up. The delayed onset participants were more symptomatic at the time of the initial interview than the controls. The delayed onset participants had poorer social support than the controls prior to and after the MVA. For the month prior to the MVA, the delayed onset participants had lower Global Assessment of Functioning scores than the controls.