The irrational use of antibiotics is incriminated for the escalating antimicrobial resistance problem worldwide. This cross-sectional survey was conducted to describe patterns of antibiotic use in community-based pediatric outpatients in the southern region of Brazil. A sample of children (29 days to 18 years of age) was selected from each community-based outpatient clinic. Information related to antibiotic use in the child was obtained by interview with their parents using a structured questionnaire. Of 489 children, 201 (41.1 per cent) had received at least one antimicrobial course in the previous 2 months. The most commonly prescribed antibiotic was amoxicillin (54.0 per cent) and broad-spectrum agents were used in 15.3 per cent of antimirobial courses. Acute respiratory infections were the most frequent diagnosis for antibiotic prescribing (91.2 per cent), but at least 39.5 per cent were conditions of presumed viral etiology. Antibiotic use in the previous 2 months was more likely in children younger than 2 years (PR 1.36, 95 per cent CI 1.10-1.69); with chronic diseases (PR 1.38, 95 per cent CI 1.10-1.75); with higher paternal education level (PR 1.38, 95 per cent CI 1.11-1.72); with parents' pressure on physician for antibiotics (PR 1.66, 95 per cent CI 1.05-2.64) and with parental self-prescribing habit (PR 1.47, 95 per cent CI 1.06-2.04). Antibiotic use in children increased with mother's age (p=0.03 for linear trend). In conclusion, antibiotic prescribing is very common in community-based pediatric outpatients in the southern region of Brazil and inappropriate use is frequent. The independent risk factors for antibiotic use are child's age under 2 years, the presence of chronic diseases in the child, older mother, higher paternal education level, parents' pressure on physician and parental self-prescribing habit.