Progesterone is a steroid hormone (C21steroid, pregn-4-ene-3, 20 dione) and is synthesized from both tissue and circulating cholesterol. The principal production sites are the adrenals and ovaries and placenta during pregnancy. The majority of this steroid is metabolized in the liver to pregnanediol and conjugated as a glucuronide prior to excretion by kidneys. The primary role is played in reproductive organs. In males the progesterone plays an intermediary role in the synthesis of corticosteroids and androgens. In females, progesterone remains relatively constant through follicular phase of ovulation. Then the levels increase following ovulation and remains elevated for4-6 days decreasing to the base line 24 hours before the onset of cycle. In pregnancy, placental progesterone raise 10-30 times those of the luteal peak levels. In females, the measurement of progesterone is useful in evaluating the status of ovarianfunctions. Monitoring of progesterone therapy and early stage pregnancy evaluations comprise the remainder of progesterone assays. During early ovarian maturation progesterone levels increase progressively in girls, in parallel with increases in gonadotropins. The importance of sequential progesterone measurements for monitoring ovulation induction, particularly in ''in vitro'' fertilization programs has recently been reported. The monitoring of LH and progesterone will help the breeders.