1. 1. Seasonal effects of neurohypophyseal hormone (oxytocin or vasopressin) action on water and Na transport across the skin and urinary bladder have been studied in frogs ( R. temporaria) inhabiting temperate zones and in toads ( B. marinus) inhabiting subtropical zones. 2. 2. The osmotic water transport across the skin in intact frogs immersed in distilled water and treated with oxytocin (10i.u./100g body wt) was approximately 50% greater during cold months (October–March) than during warm months (April–September). 3. 3. The glycogen content of the frog skin was significantly higher during cold months (86g/100g wet tissue) than during warm months (38g/100g wet tissue). However, the skin water, Na and K contents showed no seasonal variation. 4. 4. Short-circuit current response to vasopressin (250 mU/ml) in isolated toad skin and osmotic water transport response to vasopressin (100mU/ml) in isolated toad urinary bladder showed no significant seasonal variation. 5. 5. Glycogen content of liver and muscle and plasma levels of glucose, Na, K, and osmolality showed no seasonal variation in the toad. 6. 6. These results taken together with our previous findings (Hong et al. Am. J. Physiol. 215, 439–443, 1968) strongly suggest that variations in the effect of neurohypophyseal hormone on water and Na transport in amphibian preparation may be attributed to seasonal variations in tissue metabolic energy stores.