OBJECTIVE: To assess the use of complementary and alternative medicine (CAM) providers and the associated expenditures by specific treatment phases among patients with cancer. STUDY DESIGN: Cross-sectional analysis of medical services utilization and expenditures during the 3 therapeutic phases of initial, continuing, and end-of-life life treatment. METHODS: Analysis of an insurance claims database that had been matched to the Washington State Surveillance, Epidemiology, and End Results cancer registry. RESULTS: Of 2900 registry-matched patients, 63.2% were female, the median age was 54 years, and 92.7% were of white race/ethnicity. Breast cancer was the most frequent diagnosis (52.7%), followed by prostate cancer (24.7%), lung cancer (10.1%), colon cancer (7.0%), and hematologic malignancies (5.6%). Patients using CAM providers represented 26.5%. The proportion of patients using CAM was similar during each treatment phase. All patients used some conventional care. Age, female sex, breast cancer diagnosis, and white race/ethnicity were significant predictors of CAM use. Diagnosis of a musculoskeletal problem occurred at some time during the study for 72.1% of patients. CAM provider visits represented 7.2% of total outpatient medical visits, and 85.1% of CAM visits resulted in a musculoskeletal diagnosis. Expenditures for CAM providers were 0.3%, 1.0%, and 0.1% of all expenditures during the initial, continuing, and end-of-life phases, respectively. CONCLUSIONS: For patients with cancer, musculoskeletal issues were the most commonly listed diagnosis made by a CAM provider. Although expenditures associated with CAM are a small proportion of the total, additional studies are necessary to determine the importance that patients place on access to these services.