The complementary and alternative medicine (CAM) is the set of health care systems, practices and products thats are not part of conventional medicine. In our work, we stadied its use by a population of patients with ankylosing spondylitis (AS), followed in hospital or consultation. We looked at the prevalence of use, types of therapies used, reasons for the use and the doctor-patient relationship was analyzed on the existence and quality of dialogue concerning the CAM. Of the 110 patients included in this study, 72.7% used at least once in their lives CAM, 54% said they had started using it when their AS was announced and 23% of patients used CAM before knowing about their disease. 75% of patients reported using CAM for the healing purpose, 18.80% to relieve symptoms. 81.3% followed the advice of those around for the choise of CAM. Regarding the types of CAM, 75% of patients used medicinal plants in ingestion, 67.50% used massage with or without application of a product, 56.30% used spa treatments, and 40% of patients used to have sand baths and acupuncture. About the ingested products, natural honey was used by 56.30% of patients, 55% used black cumin, 25% of ingested plant mixtures of unknown composition, 18.75% used the caper and 12.50% the ginger. 75% of patients did not inform their doctor about their use of CAM, 89% of them said that they have never done it because they have not been asked to do so. Users and non users of CAM do not differ in age, sex or background… However, the practice of profession (p=0.001) and high level of education (p=0.02) are predictors of the use of CAM