The changes of anxiety in rat strain KHA (active coping style) and strain KLA (passive coping style) during the estrous cycle and progesterone levels in blood plasma were studied. Anxiety was measured by the time spent in open arms of the elevated plus maze. Plasma progesterone was determined by radioimmunoassay. KLA rats have no significant changes in anxiety during estrous cycle. KHA rats showed significant variation of anxiety during estrus cycle: high in diestrus, and low in proestrus. KHA rats showed an anxiety levels in diestrus significantly higher than KLA rats. Rats KLA progesterone levels were higher than the KHA rats, both during diestrus and proestrus. Therefore, data shows near linear negative correlation between anxiety level and plasma progesterone in rats of two strains.