BACKGROUND Hyperprolactinaemia was found to be an important cause of infertility in early seventies. Despite adequate release of gonadotropic hormones, in the presence of hyperprolactinaemia, ovulation fails to occur. Suppression of prolactin concentration to normal led to resumption of normal menstrual pattern. The aim of this study was to find out the association between serum prolactin and infertility in females of reproductive age group. MATERIALS AND METHODS In this prospective study, fifty females of reproductive age group with irregular periods were selected as cases; control group comprised fifty females of reproductive age group with regular periods. The parameters studied were body mass index, recent weight gain, dysmenorrhoea, dyspareunia, hirsutism, galactorrhoea and serum prolactin. Estimation of serum prolactin was done using Coat-A-Count prolactin IRMA, an immunoradiometric assay designed for the quantitative measurement of prolactin in serum. Statistical analysis done using Pearson Chi square test. Settings and Design-Prospective longitudinal study. RESULTS Cases with BMI greater than 25 were 38%, recent weight gain 42%, hirsutism 38%, dysmenorrhoea 84%, dyspareunia 24%, galactorrhoea 12%. 22% cases show higher prolactin levels, out of these 12% only presented with galactorrhoea. CONCLUSION Serum prolactin has a definite role in infertility.