Child safety seat misuse is still a concern in the nation. This paper addresses the patterns of child safety seat (CSS) misuse and reports on the techniques used to effectively collect this data. CSS use and misuse observations were collected for 5900 target young children (under 27 kg or 60 pounds) in over 4000 vehicles in four states:​ Mississippi, Missouri, Pennsylvania and Washington. Results showed overall CSS use for target children was 50.6%. Only 12.8% of these children were unrestrained, with the remainder were restrained in safety belts. Correct CSS use was defined as proper use of all of the following CSS elements:​ seat direction, vehicle safety belt routing, harness buckle and harness strap, harness retainer (chest) clip, and locking clip (on safety belt). Overall correct CSS use was 20.5%. For infants (children under 9 kg or 20 pounds), 96.6% were in a CSS and 20.6% of these were correctly used. For toddlers (children between 9 and 18 kg or 20 and 40 pounds), 67.5% were in a CSS and 18.9% of these were correctly used. For pre-school children (between 18 and 27 kg or 40 and 60 pounds), 6.1% were in a CSS and 50% of these were correctly used. The strongest positive relationship between target child restraint use and CSS proper use was for drivers using safety belts. Other positive relationships were found for the vehicle having air bags, the driver being a family member, the child in the middle back seat position, and CSS infrequently removed from the vehicle.