Biofeedback is the use of sensitive detectors (instruments) with visual and auditory displays to reveal to an individual minute changes in his internal physiological functions. Biofeedback training with such instruments results in the ability to voluntarily regulate physiological functions formerly believed involuntary. These physiological functions are correlates of psychological states and processes. Hence, psychological self-regulation, self-awareness, and enhancement (psychological health) are outcomes of biofeedback training for voluntary self-regulation of physiological functions. This paper presents a brief introduction to biofeedback instruments most frequently used in counseling; to counseling applications, outcomes, and cautions; and presents a rationale for counseling via biofeedback training. (Author)