Objectives: To evaluate the robustness of the Intervention Modelling Experiment (IME) methodology as a way of developing and testing behavioural change interventions prior to a full-scale trial by replicating an earlier paper-based IME. Study design and setting: Web-based questionnaire and clinical scenario study. General practitioners across Scotland were invited to complete the questionnaire and scenarios, which were then used to identify predictors of antibiotic prescribing behaviour. These predictors were compared with the predictors identified in an earlier paper-based IME and used to develop a new intervention. Results: 270 general practitioners completed the questionnaires and scenarios. The constructs that predicted simulated behaviour and intention were: attitude, perceived behavioural control, risk perception/anticipated consequences and self-efficacy, which match the targets identified in the earlier paper-based IME. The choice of persuasive communication as an intervention in the earlier IME was also confirmed. Additionally, a new intervention, an action plan, was developed. Conclusions: A web-based IME replicated the findings of an earlier paper-based IME, which provides confidence in the IME methodology. The interventions will now be evaluated in the next stage of the IME, a web-based, randomised controlled trial.