The functional status of the hypothalamo-pituitary-gonadal axis was investigated in 127 women with anovulatory disease. Radioimmunoassayable circulating LH, FSH, and prolactin concentrations were measured. An attempt was made to localize the functional lesion by utilizing the following criteria: 1. Hypothalamic function: a) clomiphene test based upon hormonal parameters; b) recording of the pulsatile LH fluctuation (spiking) and of basal FSH. 2. Pituitary function: determination of the gonadotropin reserve by means of a standardized LRH test. 3. Ovarian function: a) measurement of plasma E2 and progesterone levels by RIA; b) gestagen bleeding test. All patients had amenorrhea of up to 14 years duration. A total of 17 hyperprolactinemic patients (13.4%) was found. Eight of these patients never experienced galatorrhea, in 7 only transient galactorrhea was reported, and in 2 cases galactorrhea persisted. All hyperprolactinemic patients were found to be clomiphene non-responders as well as nonspikers. The pituitary LH reserve varied from practically none to normal. Baseline LH was low whereas that of FSH was normal. In accordance with this observation E2 levels, with two exceptions, were found to be in the lower range of normal female concentrations. Thus, all but two patients exhibited gestagen withdrawal bleeding. In conclusion, the hyperprolactinemic anvoluatory syndrome is not necessarily associated with galactorrhea. In all cases of amenorrhea syndromes with or without galactorrhea, hyperprolactinemia should be excluded as it is very often associated with anovulation. The hyperprolactinemic anovulatory syndrome includes the following features: 1. gestagen withdrawal bleeding. 2. subnormal to normal E2 levels. 3. clomiphene nonresponsiveness. 4. LH-hypogonadotropism. 5. lack of LH secretory episodes. 6. FSH-normogonadotropism.