The effects of sodium cromoglycate (SCG) on cardiovascular and pulmonary responses to phenylbiguanide, capsaicin, and vagal stimulation were studied in anesthetized guinea pigs. Phenylbiguanide had no bronchospastic activity but induced reflex changes in arterial blood pressure which were reduced or abolished by SCG. Capsaicin induced nonreflex bronchospasm, and decreases in arterial blood pressure that were unaffected by SCG. Sodium cromoglycate, given before or after atropine, had no effect on the bronchospasm and cardiovascular responses to unilateral or bilateral stimulation of the vagus nerves. We conclude that SCG may influence both the afferent and efferent pathways of responses to drugs.