Abstract (1) Female hamsters which received 500 μg testosterone propionate (TP) at 12 or 24 hr after birth displayed the male orienting response and copulatory pattern towards a lure female with frequencies and durations of response similar to those found in the normal male. (2) Injection of 250 μg estradiol benzoate (EB) at 12 or 24 hr after birth also resulted in the treated females displaying the male level of response towards a lure female for all elements of behavior measured except intromission. (3) Injection of either TP or EB at 48, 72, 96 or 120 hr after birth was less effective than 12 or 24 hr treatment for induction of the male orienting and copulatory pattern in the treated female. (4) Male hamsters given similar EB or TP treatment between 12 and 120 hr after birth showed no change in orienting or copulatory behavior towards a lure female. (5) All behavioral measures were made while the treated females were intact and not receiving any exogenous hormone treatment. This indicates that expression of the male orienting response and copulatory pattern by the female hamster as a result of neonatal steroid treatment (organizational event) is not dependent upon a series of hormone injections (activational event) in the adult animal.