A treatment that is not recognised as conventional medicine is frequently referred to as part of complementary and alternative medicine (CAM) methods. This Chapter will provide an overview of the several CAM definitions currently proposed and the types of CAM methods. The prevalence of CAM use and the characteristics and attitudes of CAM users will be also explored with a focus on patients with kidney diseases. The reasons for CAM use and the literature on the placebo effects as a debated hypothesis of CAM mechanism of action is presented.