Objective: To acquire information for designing a large clinical trial and determining its feasibility and to make preliminary estimates of the relationship between headache outcomes and the number of visits to a chiropractor. Design: Randomized, controlled trial. Setting: Private practice in a college outpatient clinic and in the community. Subjects: Twenty-four adults with chronic cervicogenic headache. Methods: Patients were randomly allocated to 1, 3, or 4 visits per week for 3 weeks. All patients received high-velocity low-amplitude spinal manipulation. Doctor of Chiropractics could apply up to 2 physical modalities at each visit from among heat and soft tissue therapy. They could also recommend modification of daily activities and rehabilitative exercises. Outcomes included 100-point Modified Von Korff pain and disability scales, and headaches in last 4 weeks. Results: Only 1 participant was insufficiently compliant with treatment (3 of 12 visits), and 1 patient was lost to follow-up. There was substantial benefit in pain relief for 9 and 12 treatments compared with 3 visits. At 4 weeks, the advantage was 13.8 ( P = .135) for 3 visits per week and 18.7 (P = .041) for 4 visits per week. At the 12-week follow-up, the advantage was 19.4 (P = .035) for 3 visits per week and 18.1 (P = .048) for 4 visits per week. Conclusion: A large clinical trial on the relationship between pain relief and the number of chiropractic treatments is feasible. Findings give preliminary support for the benefit of larger doses, 9 to 12 treatments, of chiropractic care for the treatment of cervicogenic headache.