To examine antimicrobial prescribing rates for viral respiratory tract infections by primary care pediatricians in the greater Toronto area, charts were reviewed for the week of 17-21 February 1997 at 61 pediatricians' offices. Antibiotics were considered appropriate if the diagnosis was compatible with bacterial infection. A total of 3,585 patient visits were reviewed. The common cold was the most common respiratory tract syndrome leading to an office visit (1,317 visits). The overall rate of appropriate antibiotic prescribing was 89.5%. There was no significant difference in prescribing when physicians were compared by year of graduation from medical school, sex, or location of training. Diagnostic codes (ICD-9 [International Classification of Diseases, 9th edition] codes) did not match the chart diagnosis in 41% of cases. Toronto primary care pediatricians appear to have a lower rate of inappropriate antibiotic prescribing than do primary care physicians in other regions of Canada and the United States.