Our aim was to evaluate effects on prescribing for urinary tract infection (UTI) and asthma, of an education with messages based on national guidelines, aimed at improving prescribing in primary care in Sweden. The study is part of the European Drug Education Project. A randomized controlled trial, with groups of general practitioners (GPs) allocated to education on UTI (18 groups, 104 GPs) or asthma (18 groups, 100 GPs), the two parallel intervention arms being controls for each other. Feedback was provided on the GP's judgments of simulated cases and prescribing. Prescribing indicators were developed and measured before and after the intervention. Analysis was performed by multi-level technique. Prescribing of first choice UTI drugs increased in the intervention arm from 52% to 70% and remained constant in the control arm (P < 0.001). The proportion of patients receiving an inhaled corticosteroid increased insignificantly in both study arms. The educational model can be used to improve prescribing. Further studies are needed to define when the model is effective.