Seventeen healthy women (21-31 years) not taking oral contraceptives were tested at three phases of the menstrual cycle distinctly differing in hormonal patterns (menses, preovulatory phase, and midluteal phase). Phase detection was assured by determination of blood hormone concentrations. Another 17 women taking oral contraceptives (combined preparation of estrogen and progestin) served as age-matched controls, and were tested during menses and during phases corresponding to preovulatory and midluteal phase. On each test occasion, aspects of creativity were assessed by a battery of six tests measuring "semantic" and "figural" abilities of divergent thinking. Additionally, a test of motor perseveration (Mittenecker-Zeigeversuch) was presented. During the preovulatory phase, creativity was in general improved when serum concentrations of estrogen (E2) and luteinizing hormone (LH) were highest whereas motor perseveration decreased. In control women, there was no preovulatory improvement of divergent thinking and no preovulatory decrease in motor perseveration.