Summary. The concentrations of LH, FSH, prolactin, oestradiol and progesterone in serum were measured daily during the menstrual cycle of 100 normal Chinese women. The cyclic changes in LH, FSH, oestradiol and progesterone were typical of ovulatory cycles in women of other ethnic groups as reported in the literature. The geometric mean of the LH midcycle peak value was 51·64 i.u./l, the FSH mid-cycle peak value was 11 ·52 i.u./l, the preovulatory oestradiol peak was 1229·12 pmol/1, and the progesterone luteal maximum was 53·27 nmol/1. The cyclic changes of prolactin concentrations were irregular: the value at mid-cycle was significantly higher than that at the follicular or luteal phases.
A correlation between the length of the cycle and mean concentrations of LH and oestradiol at different stages throughout the cycle was shown.