Background. The extent of use of antibiotics to treat upper respiratory infections in general practice is an area for concern due to the increasing problem of bacterial resistance. Effective educational strategies to promote rational prescribing are needed. Objectives. We aimed to examine the effectiveness of prescriber feedback and management guidelines in reducing antibiotics prescribing by GP trainees for undifferentiated upper respiratory tract infection, and in improving the choice of antibiotic for tonsillitis/streptococcal pharyngitis. The research tested a stepwise approach to targeting educational input to high prescribers. Method. General Practice trainees in New South Wales (n = 157) were randomly allocated to a treatment group (n = 78) which received an education intervention on antibiotic use, or to a control group (n = 79) which received an intervention on an unrelated topic. Trainees completed three practice activity surveys, each of 110 consecutive patient encounters, with 6-month intervals between surveys. Prescriber feedback and management guidelines on use of antibiotics for URTI and choice of antibiotic for tonsillitis/streptococcal pharyngitis were delivered in a written form between surveys 1 and 2. An educational outreach visit to high prescribers occurred between surveys 2 and 3. Outcome measures were the rate of antibiotic prescribing for all indications, for URTI and prescribing of select antibiotics for tonsillitis/streptococcal pharyngitis. Results. Antibiotic prescribing by the intervention group declined over three occasions from 25.0 to 23.3 to 19.7 per 100 URTI problems, while the control group increased from 22.0 to 25.0 to 31.7 per 100 URTI problems (P = 0.002). Prescribing in agreement with accepted guidelines for tonsillitis/streptococcal pharyngitis increased over time in the intervention group from 55.6 to 69.8 to 73.0 per 100 problems, but decreased in the control group from 59.6 to 57.5 to 58.5 (P = 0.05). Conclusion. Prescriber feedback and management guidelines were shown to influence antibiotic prescribing for URTI and choice of antibiotic for tonsilitis/streptococcal pharyngitis. This study provides a model for targeting educational input to those prescribers who most need to change their behaviour.