Prescribing practices for respiratory infection during the first three years were studied in a birth cohort of Christchurch children. Of the 5630 consultations studied 39 percent were treated with antimicrobial therapy only, 23 percent by antimicrobials supplemented by other medication, 22 percent by other medication only and 16 received no medication. There were only 27 return consultations because of the iatrogenic effects of medication prescribed for respiratory infection and all of these involved adverse reactions to antimicrobial treatment. However, in no case did these reactions require further treatment other than withdrawing or changing the child's medication. The implications of the high rate of antimicrobial prescribing present for this sample are discussed.