One group of 20 males was told that tensing the pelvic musculature would enhance sexual responsiveness (tension-good), while another group of 20 males was told that relaxation would increase responsiveness (relaxation-good). Using feedback to regulate EMG to predetermined levels, subjects were required in a counterbalanced design to tense and relax while viewing one of two matched series of 14 erotic slides interspersed with neutral slides. Expectancy and induced tension or relaxation both affected penile response: Relaxation was accompanied by lower levels of penile volume response to slides than was tension but only in the relaxation-good group. A similar pattern of means was shown in scores on a general arousal factor with virtually equal contributions from respiration rate, respiration amplitude, and heart rate. These data are interpreted to show that tension enhanced responsiveness irrespective of induced expectancy but that the effect of relaxation depended upon whether subjects were (correctly) informed that tension was conducive to greater response. Over subjects and conditions, penile volume was poorly correlated with the other physiological measures.