We compared the survival of 658 seriously injured patients treated in Los Angeles County in the Fall of 1982 (prior to the activation of the trauma system) with that of 766 such patients treated in the Fall of 1984 (when the system was young and composed of essentially a full complement of trauma centers). We demonstrated a statistically significant improvement in the adjusted odds of survival for 1984 over 1982 with regard to victims of motor vehicle collisions who sustained multiple serious injuries (1980 Injury Severity Score: 26–50) (p = 0.042). For the data set as a whole, although an improvement in survivorship over this period was suggested by the data, statistical significance could not be demonstrated.