This paper characterizes the field performance of occupant restraint systems designed with advanced air bag features including those specified in the US Federal Motor Vehicle Safety Standard (FMVSS) No. 208 for advanced air bags, through the use of Event Data Recorders (EDRs). Although advanced restraint systems have been extensively tested in the laboratory, we are only beginning to understand the performance of these systems in the field. Because EDRs record many of the inputs to the advanced air bag control module, these devices can provide unique insights into the characteristics of field performance of air bags. The study was based on advanced air bag cases extracted from NASS/CDS 2000-2005 with associated EDR data. The paper presents the characteristics of advanced air bag deployment (number of stages and trigger time) as a function of crash severity and seating location, the characteristics of delayed deployments, and the frequency and characteristics of frontal crashes in which the air bag did not deploy.