OBJECTIVES: General practitioners (GPs) in the UK continue to prescribe antibiotics for patients with sore throats despite evidence that they are ineffective and can contribute to the growth of antibiotic resistance in the population. This study uses the theory of planned behaviour (TPB) to investigate the strength of intention to prescribe antibiotics, and to identify the salient beliefs associated with this intention. DESIGN: Cross-sectional study testing hypotheses derived from the TPB. METHOD: A 66-item postal questionnaire was distributed to a random sample of GPs in one NHS region (N = 185). The questionnaire included measures of intention to prescribe antibiotics, attitude, behavioural beliefs and evaluations, normative beliefs and evaluations, perceived behavioural control, control beliefs, and past prescribing. RESULTS: Two-thirds of the GPs returned complete questionnaires (N = 126, 68%). The majority intended to prescribe antibiotics for less than half of their patients with sore throats (N = 69, 55%). The variables specified in TPB predicted 48% of the variance in intention, with past behaviour adding a further 15%. Seven salient beliefs distinguished between doctors who intend to prescribe antibiotics and those who do not. CONCLUSIONS: Attitudes towards antibiotics and control beliefs are important predictors of intention to prescribe, as predicted by TPB. Interventions could target salient beliefs associated with motivation to prescribe.