Cancer patients who had developed negative conditioned responses to their chemotherapy either did (relaxation training) or did not (no relaxation training) receive progressive muscle relaxation training and guided relaxation imagery instructions immediately before and during their chemotherapy treatments. Physiological (blood pressure and pulse rate) measures of arousal, frequency of vomiting, and patient-reported and nurse-reported indices of negative affect and nausea were collected during pretraining, training and posttraining chemotherapy sessions. Results indicated that during both the training and the posttraining sessions, patients in the relaxation training condition reported feeling less emotionally distressed and nauseated, and showed less physiological arousal following the chemotherapy infusion, than patients in the no relaxation training condition. The attending nurses' observations confirmed the patients' self-reports. No differences were found in frequency of vomiting between conditions. These data clearly suggest that the use of relaxation procedures may be an effective means of reducing several of the adverse side effects of cancer chemotherapy.