The principles of R-S learning were applied to a 32-yr.-old Caucasian woman to reduce the frequency and duration of fingernail-biting activity in a reversal-replication (ABAB) research design. The undesirable behavior, fingernail-biting which included frequency and duration, antecedents, and setting events, was recorded during a 28-day study. Self-monitoring recordings indicated that anxiety was the most prevalent antecedent. Through the use of a preliminary questionnaire and interview, increase in self-awareness was judged to be most effective in the extinction of the undesired behavior. The systematic desensitization techniques of deep muscle relaxation and Transcendental Meditation were used during the treatment phase.