Objective: This study aims to determine the effectiveness and efficiency of a national accreditation and improvement programme for general practice, focusing on patients with established cardiovascular diseases.

Design: Cluster randomised trial with a block design. All practices start with the accreditation procedure.Intervention group practices are requested to focus their improvement plans in the first year on cardiovascular disease. Control group practices are requested to focus their improvement plans in the first year on other domains. Measurements at baseline are based on the standard audit in the accreditation procedure. Follow-up measurements are done 12 months after approval of improvement plans.

Participants: Primary care physicians in The Netherlands.

Interventions to be implemented: improvement plans concerning cardiovascular risk management, as described by recently updated national multidisciplinary evidence-based NHG / CBO guidelines, considering patients with established cardiovascular diseases.

Implementation strategy: The national programme for accreditation and improvement of general practice. This procedure consists of a package of activities, including audit, feedback, improvement plans, and follow-up.

Outcome measures: Primary outcomes are percentages of patients with CVD who have acceptable systolic blood pressure and cholesterol levels (quantified according to the indicators in the accreditation)and who use aspirin or alternatives. Secondary measures include clinical and organisational indicators of quality of cardiovascular care, such as percentages of patients with cardiovascular disease whose risk factors were assessed and who received specific medication.

Economic evaluation: Incremental cost effectiveness ratio's are determined of the implementation strategy compared to no implementation. The analysis will take a societal perspective and a time horizon of the observed period as well as a hypothetical 10 years period (using modelling). Uncertainty related to the estimations is examined with sensitivity analyses and bootstrapping. The long term economic evaluation is based on Markov modelling.

Inclusion Criteria:

• Patients with established cardiovascular diseases (myocard infarct, angina pectoris, cerebrovascular accident, Transient Ischaemic Attack, peripheral vascular disease, aneurysma aortae)

Exclusion Criteria:

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