OBJECTIVES: To estimate for the United Kingdom (UK) and France the first year diabetes-related costs of naive patients with type 2 diabetes initiated upon therapy with the same oral hypoglycemic agent (Diamicron). In both the UK and France, responsibility for the care of patients with type 2 diabetes rests with general practitioner physicians. METHODS: Patient records of consecutive naive patients were collected from general practices (two in the UK, one in France). Diabetes-related resource utilization and costs for the first year post-initiation of oral therapy were analyzed. This included medication, professional visits, hospital outpatient visits, emergency visits, inpatient hospitalizations, laboratory tests and procedures, and self-administered tests. RESULTS: Healthcare utilization and concomitant costs (denominated in the Euro) for naive type 2 diabetic patients initiated on Diamicron varied greatly between these practices in the UK and France. The biggest difference in utilization was greater use in France of hospital inpatient and hospital outpatient services. Total annual direct medical costs in France were approximately 1,620 Euro (10,600FF), compared with 454 Euro (320 BP) in the UK. Costs of Diamicron, as actually prescribed and used by the patients, also varied considerably: 112 Euro in France versus 65 Euro in the UK. CONCLUSION: Patient care and associated costs for patients newly diagnosed with a common clinical condition such as diabetes can vary considerably even within populous western European nations. Analyses of cost of illness and cost effectiveness must be careful to use country-specific data in order to maximize the utility of these analyses by relevant decision-makers within those countries.