The theoretical basis for Wolpe's systematic desensitization, with its principle of reciprocal inhibition and its emphasis on the role of physiological relaxation, is explained. The author examines the literature relevant to the effectiveness of desensitization with, and without, relaxation, as well as the effectiveness of relaxation alone. All 3 areas of emphasis are found to be supported by current research, thus producing a dilemma: relaxation vs. desensitization? Two attempted theoretical rapprochements are brought to bear on the problem, both of which call into question Wolpe's neurophysiological explanation of the principle of reciprocal inhibition. Is it actual physiological relaxation (musculature) or is it cognitions which account for the success of desensitization? Other problem areas encountered in the use of relaxation and desensitization are explored. In a final, brief section, the author discusses the practical implications which these techniques have for counselors. (TL)