This paper describes characteristics of child safety seat misuse among attendees at 41 inspections held between February 1999 - April 2001 in San Diego County, CA. Standardized criteria were assessed by certified technicians. These 41 events consisted of 988 inspections for proper installation and adjustment. 963 had a determined seat type (rear-facing, forward facing, belt positioning boosters, shield boosters, other restraint, vehicle safety belts). Each seat type had specific criteria for misuse ranging from 3 to 15 measures. 95.6% had at least one error, which could reduce the seat’s protection of its occupant from injury in a crash.