The effectiveness of child-resistant closures, required under the Poison Prevention Packaging Act of 1970, in reducing the incidence of accidental ingestion of aspirin and aspirin-containing products among children less than 5 years of age has been investigated. Data from Poison Control Centers and the National Center for Health Statistics were analyzed to determine the ingestion level before and two to three years after safety closures were required. Baby aspirin and nonbaby aspirin products were analyzed separately. For baby aspirin, it is estimated that safety packaging has reduced the incidence of ingestions 45% to 55%. For nonbaby aspirin products, the reduction has been 40% to 45%.