A telephone survey was conducted of 356 patients with colon, breast, or prostate cancer identified from the population-based Cancer Surveillance System of western Washington, USA. Overall, 70% of patients used at least one type of alternative medicine, with 16.6% seeing alternative providers, 19.1% using mental or other therapy, and 64.6% taking dietary supplements. Compared with males, females were five times more likely to see an alternative provider and about twice as likely to use mental therapies or supplements (P < 0.05 for all). Older patients were less likely to use mental or other therapy. Higher education (but not income) was associated with use of all types of alternative medicine. Patients with multiple medical treatments were twice as likely to take dietary supplements compared with patients having only surgery (P < 0.01). Varying by type of alternative therapy, 83–97% of patients reported that they used alternative medicine for general health and well-being while 8–56% reported use for treatment of cancer. Almost all patients reported that the alternative therapy improved their well-being. Expenditures for alternative medicine averaged US$68 per user per year, but ranged from $4 to $14 659.