Background Respiratory tract infections are the most common reason for antibiotic prescription in Sweden as in other countries. The prescription rates vary markedly in different countries, counties and municipalities. The reasons for these variations in prescription rate are not obvious.

Aim To find possible explanations for different antibiotic prescription rates in children.

Design of study Prospective population based study.

Setting All child health clinics in four municipalities in Sweden which, according to official statistics, had high antibiotic prescription rates, and all child health clinics in three municipalities which had low antibiotic prescription rates.

Method During one month, parents recorded all infectious symptoms, physician consultations and antibiotic treatments, from 848 18-month-old children in a log book. The parents also answered a questionnaire about socioeconomic factors and concern about infectious diseases.

Results Antibiotics were prescribed to 11.6% of the children in the high prescription area and 4.7% in the low prescription area during the study month (crude odds ratio [OR] = 2.67; 95% confidence interval [CI] = 1.45 to 4.93). After multiple logistic regression analyses taking account of socioeconomic factors, concern about infectious illness, number of symptom days and physician consultations, differences in antibiotic prescription rates remained (adjusted OR = 2.61; 95% CI = 1.14 to 5.98). The variable that impacted most on antibiotic prescription rates, although it was not relevant to the geographical differences, was a high level of concern about infectious illness in the family.

Conclusions The differences in antibiotic prescription rates could not be explained by socioeconomic factors, concern about infectious illness, number of symptom days and physician consultations. The differences may be attributable to different prescription behaviour.