This study investigated the effectiveness of child-resistant closures, required under the Poison Prevention Packaging Act of 1970, in reducing the incidence of accidental ingestions of 15 regulated substances among children less than 5 years of age. The regulated substances include aspirin, acetaminophen, prescription drugs, and household chemicals. Data from the National Electronic Injury Surveillance System and the National Center for Health Statistics were analyzed to determine ingestion and death rates associated with these substances over a five-year-period. The ingestion rate for all substances that require child-resistant closures has declined from 5.7/1,000 children in 1973 to 3.4/1,000 children in 1978. It is estimated that child-resistant closure have prevented nearly 200,000 accidental ingestions since 1973. Over the past 20 years, the death rate due to poisonings of children has declined from 2.0/100,000 children to 0.5/100,000.