Intravenous drug users often have many health conditions in addition to their drug addiction, yet may be isolated from conventional sources of care. They have never before been examined for their use of complementary and alternative medicine (CAM) therapies. Our purpose was to study the prevalence and predictors of CAM use among persons with a history of intravenous drug use through a cross-sectional survey of intravenous drug users examining their utilization of health services, including CAM therapies. A total of 548 persons with a history of intravenous drug use, recruited from a needle-exchange program and a methadone maintenance clinic, both in Providence, Rhode Island, participated. Overall prevalence of any CAM use in the past 6 months, frequency of use of individual named CAM therapies and domains, and demographic and clinical characteristics associated with CAM users, reasons for CAM use and self-perceived effectiveness of CAM were also measured. Of the 548 participants, 45% reported use of at least one CAM therapy. The top three therapies--religious healing, relaxation techniques, and meditation--were all from the mind-body domain. Having a higher education and lower self-rated health were the two strongest predictors of CAM use, followed by having a regular doctor or clinic, being white and younger. There was a high level of self-perceived effectiveness of CAM therapies (4.1 on a scale of 1-5), and CAM users were likely to use CAM for reasons related to their addiction.