Renal (Na + K)‐ATPase was studied to ascertain whether it follows the pattern of adaptation of membrane‐bound enzymes that are inhibited by acute ethanol exposure and develop greater activity after chronic ethanol treatment. A colony of rats was given 20 per cent (v/v) ethanol as sole drinking solution throughout gestation, lactation and following weaning. (Na + K)‐ATPase and ouabain‐insensitive Ca2+‐ATPase activities were determined; regional distribution of these enzymes was assessed in renal cortex and outer medulla. Control rats drank tap water. (Na + K)‐ATPase in whole homogenate of kidney increased with age in controls and ethanol‐fed rats, but the latter showed higher values at every age studied. Between 15 and 60 days of age, the control group showed 2‐fold increases in cortex and 5‐fold in outer medulla, whereas ethanol‐fed rats reached a 3‐fold increase in the enzyme activity in both renal regions. Ca2+‐ATPase showed the same time course in developing kidney of both groups. C