SUMMARY: 0·05 mg. oestradiol benzoate, injected thrice weekly alone or in combination with either 0·25 mg. progesterone or 75 i.u. prolactin, induced an increase in tactile sensitivity in the female canary's brood patch. Progesterone and prolactin alone did not produce this effect; 0·3 mg. of the oestrogen was also ineffective alone and in combination with the other hormones.