To investigate the role of brain catecholamine (CA) activity in the mechanisms related to physiological ovulatory function, we used high-performance liquid chromatography with electrochemical detector to measure the levels of urinary dopamine (DA), norepinephrine (NE), epinephrine (E), vanillylmandelic acid (VMA), homovanillic acid (HVA), 3,4-dihydroxyphenylacetic acid (DOPAC), and total 3-methoxy-4-hydroxy-phenylglycol (MHPG) in a group of 12 normal women during both the early follicular and pre-ovulatory phases of the menstrual cycle. The mean (+/- SEM) concentrations of HVA and DOPAC were significantly lower (P less than 0.001) during the pre-ovulatory phase than during the early follicular phase, whereas those of DA, NE, E, VMA and total MHPG were unaltered. A significant negative correlation between urinary HVA and plasma LH (r = -0.70, P less than 0.01) was also found during the pre-ovulatory period, whereas no significant negative correlations were found between urinary HVA and plasma PRL, progesterone and oestradiol. These data show: 1) reduced brain DA activity and 2) unchanged brain NE activity at the time of the midcycle surge in normal women, suggesting a physiological variation of the central DA metabolism in ovulatory function.