Whether an individual's state of mind can influence the body's immune system has been studied for several decades. Historical notions of a homeostatic, self-contained, and self-monitored system have been discarded. Studies have explored conditioning effects and cognitive behavioral methods to affect the immune response. This study is based on the assumption that relaxation imagery can be used as an endogenous means to produce specific physiological change in the immune function. Subjects were instructed to make a directional change in the absolute number of peripheral lymphocytes using relaxation imagery.