Background: Respiratory tract infections are common in general practice: antibiotics and symptomatic drugs are frequently prescribed for these conditions. Since most respiratory tract infections are of viral origin, there is no conclusive evidence of usefulness of such medication. The reasons for general practitioners' (GPs') prescribing behaviour are not well understood.Objective: To assess the influence of medical and nonmedical factors on antibiotic and symptomatic drug prescription for respiratory tract infections: the common cold, sinusitis, tonsillitis, laryngitis and bronchitis.Methods: Eighteen GPs recruited all the adult patients (maximum n=30) who consulted them with symptoms of respiratory tract infection during a two-week period. Information on patients was obtained from matched physician-patient questionnaires completed for each patient, or in case of non-responding patients, from the GP questionnaire only. The patient forms focused on symptoms, reasons for consulting and expectations; whereas the physician documentation concentrated on diagnosis, prescriptions and pre-existing chronic conditions. The predictors of antibiotic and symptomatic drug prescriptions were identified by univariate and multivariate analyses.Results: A total of 417 physician questionnaires including 280 matched doctor-patient questionnaires were obtained, 35 GP cases (27 matched pairs) were excluded from the analysis because of a principal diagnosis other than a respiratory tract infection.Antibiotics were prescribed for 106 of 382 patients (27.7%); and cough and cold preparations for 67%. Tonsillitis (odds ratio [OR]: 216.65), bronchitis (OR: 3.44), sinusitis (OR: 2.48) and yellow-green sputum (OR: 4.44) and not being a current smoker (OR: 0.2) significantly predicted antibiotic prescriptions.Patients' wish for a symptomatic drug (OR: 18.84), bronchitis (OR: 3.43), yellow-green sputum (OR: 2.34) and not having tonsillitis (OR: 0.10) predicted prescription of symptomatic drugs.Conclusion: The diagnosis of a presumed bacterial infection is important for a GP's decision to prescribe antibiotics, even though many of these patients probably have a viral disease. Patient expectations are extremely important when prescribing cough and cold drugs. For a better understanding of GPs' prescribing behaviour, a simultaneous consideration of medical and non-medical factors seems appropriate.