Background: Success in treating hypertension is greater in clinical trials than in actual practice. To prospectively study real-world antihypertension treatment patterns, therefore, naturalistic studies are essential. Objective: The primary objective of the Caring for Hypertension on Initiation: Costs and Effectiveness (CHOICE) study was to evaluate the feasibility of performing a naturalistic study in patients with newly diagnosed hypertension in terms of enrollment, adequacy, and the timeliness of data collection and study procedures. Methods: The CHOICE study prospectively collected actual practice data from physicians, who were blind to the study purpose and hypotheses, treating newly diagnosed hypertensive patients. The initial therapy was randomly assigned to either Group 1 (diuretics or beta-adrenoceptor antagonists) or Group 2 (calcium channel antagonists or ACE inhibitors). The protocol made no demands on usual medical care in scheduling visits and changing treatment during follow-up. Only a final visit at 5 +- 1 months was mandated. Direct involvement of the CHOICE study team was minimized using a remote study monitoring system to collect data and communicate with study sites. Results: Within 30 weeks, a total of 55 physicians enrolled 512 patients with a mean age blood pressure of 158/99mm Hg. In all, 46 different antihypertensive medications were prescribed and 2554 office visits (range 1-16 visits per patient) were attended. Other medical resource use was low during the study period. A final, clean database was ready for analysis 30 days after the last patient visit. Conclusion: The results of this pilot study demonstrate that CHOICE is a feasible framework within which the real-world effectiveness and cost effectiveness of initial therapy for patients with newly diagnosed hypertension can be studied. Protocol flexibility and a novel electronic data entry system are core elements of this naturalistic design.