In order to examine a possible role of adrenaline (AD) or noradrenaline (NA) in the control of lordosis behavior, lordosis quotient (LQ) was observed daily for 8 consecutive days in the ovariectomized rat given daily 1 or 2 microgram/0.1 ml oil of estradiol benzoate (EB) alone or together with 100 microgram/0.1 ml saline of AD or NA. AD but not NA treated together with EB caused a greater change in the daily LQ than the same dose of EB alone and the change in the daily LQ by daily treatment with both 1 microgram EB and 100 microgram AD was equivalent to that by daily treatment with 2 microgram EB alone. A half mg progesterone (P) could induce the lordosis behavior in the ovariectomized rat treated 48 hr prior with both 1 microgram EB and 50 or 100 microgram AD, but not in the one treated with 1 microgram EB alone. While 50, 100 or 200 microgram NA or 10 microgram AD had no effect, 50 or 100 microgram AD pretreated together with 2 microgram EB produced a markedly higher LQ after P than 2 microgram EB alone in the ovariectomized rat. This effect of AD on the induction of lordosis behavior was produced only when AD was pretreated simultaneously with EB and AD priming 24 or 43 hr after EB failed to elicit the effect. Therefore, it is suggested that a change of the brain target site in the estrogen sensitivity produced by AD plays a part in the control of lordosis behavior.