To establish the prevalence of positive penicillin skin tests among outpatients without any drug reaction history. Skin testing was performed in 147 children (aged 6–13 years) who had had received a penicillin preparation at least three times in the last 12 months without any allergic reaction. Before testing, detailed pediatric and allergy history were learned and then all children were tested with benzyl penicilloyl polylysin (PPL) and mixture of minor antigenic determinants. The test procedures were made epidermally and intradermally subsequently in every subject. The overall frequency of positive skin reactions to penicillin antigens was 10.2%. A mild systemic reaction was observed in one of the children during testing with PPL. We concluded that frequent use of penicillin and other β-lactam antibiotics leads to sensitization of children in our study population despite these children seem to be asymptomatic during testing time.