More than 300 accidental ingestions of acetaminophen products in children 6 years of age and younger have been reported to the Rocky Mountain Poison Center, Denver, during September 1974 to September 1979. Few of these have resulted in toxic reactions, based on clinical examination of the children. This report documents 17 childhood ingestions of acetaminophen in which plasma levels of the substance were measured and liver function was evaluated. Thirteen of these cases occurred as a result of accidental ingestion by children 6 years of age or younger; five of these children had documented plasma levels that were in the toxic range of an adult nomogram and were treated with acetylcysteine. Only minor abnormalities in liver function were observed in the treated children, even when therapy was instituted as late as 20 hours after ingestion.