Iprindole, an active antidepressant in clinical use, has no effect on norepinephrine reuptake and does not bind to receptors of the noradrenergic system. Iprindole weakly antagonizes reserpine hypothermia and potentiates yohimbine toxicity. This effect is antagonized by propranolol but not by atenolol or metoprolol. In an acute dose, iprindole potentiates the effect of maprotiline on yohimbine toxicity. Beta 2-adrenergic agonists and antagonists specifically modify the effect of iprindole on spontaneous motility. These results indicate that iprindole has an indirect beta 2-mimetic effect.