The study assesses posttraumatic intrusion, avoidance, and social functioning among 214 Israeli combat veterans from the first Lebanon War with and without combat stress reaction (CSR) 1, 2, 3, and 20 years after the war. CSR veterans reported higher intrusion and avoidance than did non-CSR veterans. With time, there was a decline in these symptoms. In addition, intrusion and avoidance were associated with problems in social functioning on a given year, and they longitudinally predicted social dysfunction 2, 3, and 20 years after the war. CSR veterans presented stronger temporal covariations between intrusion-avoidance and social functioning. The findings suggest that CSR is a marker for future psychopathology and point to the role of avoidance in social dysfunction.