Few studies have clarified the use of complementary therapies (CTs) in France. The main objective of this preliminary study was to evaluate knowledge of CTs in 4 representative groups of patients: patients suffering from cancer, patients presenting with a chronic noncancerous disease, chronic dialysis patients and nonchronic or cancerous patients needing surgery.A formalized questionnaire was designed by 2 psychologists, an oncologist and an anesthesiologist in charge of the Pain Clinic and Support Care Unit. One-hundred eleven patients were enrolled, and all agreed to complete the questionnaire.Eighty (72%) patients did not know the term "complementary therapies" (patients who were "not aware of CTs"), and 24 (21.6%) patients knew the term "complementary therapies" (patients who were "aware of CTs"), while 7 patients were not sure of the meaning. There were no differences between aware and unaware patients in gender (P = .27), age (P = .24), level of education (p = 0.24) or professional occupation (P = .06). Knowledge about CTs was significantly different among the different categories of patients (P = .03), with the only statistically significant difference between groups being between oncologic patients receiving ambulatory chemotherapy and patients presenting with a chronic noncancerous disease (P = .004).This preliminary study clearly highlights that patients and health caregivers are not aware of CTs and that there is a need for better communication about CTs.