The effects of two types of operant muscular relaxation, frontalis relaxation and brachio- radialis relaxation, on peak expiratory flow rate were studied in a group of 40 asthmatic children. Using a yoked control design, conditioned frontalis relaxation was shown to occur in one group of asthmatic children. These individuals exhibited increases in PEFR, whereas children in the frontalis conditioning control group showed no improvement in this variable. Conditioned brachioradialis relaxation could not be demonstrated with the training procedures currently employed. Also, in this case, neither the brachioradialis conditioning nor its yoked control group experienced PEFR changes as a result of training. The results of the present study provided support for the previous finding that frontalis muscle relaxation effects PEFR increases in asthmatic children.