Cefaclor is an oral semisynthetic cephalosporin that is popular in the treatment of infections in children. This drug has been associated with a serum sickness--like reaction characterized by an urticarial eruption, pruritus, arthritis, and/or arthralgias. We report 12 additional cases of cefaclor-related serum sickness--like reactions in children. All patients improved after discontinuation of the drug and no long-term complications resulted.