Variation in some central monoamine levels has been shown to be influenced by cyclical changes in gonadal hormones in women; however, there is less consensus about how the human menstrual cycle affects turnover of dopamine. Fluctuations in plasma homovanillic acid (HVA) are thought to represent changes in central dopamine turnover and activity and, some suggest, may be used to monitor the response to neuroleptic medication or to predict those more likely to respond to antipsychotic treatment. We have measured the effect of fluctuations in gonadal hormones on the level of plasma HVA at four consecutive points across the menstrual cycles of 30 healthy volunteers. We found no significant change in plasma HVA over the cycle and there was no correlation with either estradiol or progesterone levels. This study suggests that peripheral markers of central dopamine function do not change significantly with physiological changes in gonadal hormones levels.