OBJECTIVES: To investigate whether clinical practice guidelines in different countries take ethnic differences between patients into consideration and to assess the scientific foundation of such ethnic specific recommendations. DESIGN: Analysis of the primary care sections of clinical practice guidelines. SETTING: Primary care practice guidelines for type 2 diabetes mellitus, hypertension, and asthma developed in the USA, Canada, the UK, and the Netherlands. MAIN OUTCOME MEASURES: Enumeration of the ethnic specific information and recommendations in the guidelines, and the scientific basis and strength of this evidence. RESULTS: Different guidelines do address ethnic differences between patients, but to a varying extent. The USA guidelines contained the most ethnic specific statements and the Dutch guidelines the least. Most ethnic specific statements were backed by scientific evidence, usually arising from descriptive studies or narrative reviews. CONCLUSION: The attention given to ethnic differences between patients in clinical guidelines varies between countries. Guideline developers should be aware of the potential problems of ignoring differences in ethnicity.