['To measure serum resistin levels in infertile women undergoing in vitro fertilisation-embryo transfer (IVF-ET), and to find any correlations between serum resistin levels and body weight, body mass index, the number of oocytes retrieved, and the outcome of IVF-ET. In addition, to assess whether there is any difference in serum resistin levels between infertility caused by polycystic ovary syndrome (PCOS) and infertility caused by other female factors.', 'We designed a case-control study, and a total of 44 infertile women were enrolled. The blood samples for resistin measurement were collected on day 3 of the menstrual cycle prior to the administration of gonadotropin during in vitro fertilisation. These cases were then divided into 2 subgroups (PCOS group versus non-PCOS group) and a number of variables were measured and compared, including serum resistin levels.', 'Serum resistin levels were inversely correlated with the number of oocytes retrieved (r=-0.371, p=0.013). No significant correlation was found between serum resistin levels and body mass index or body weight, either in the whole group or in the 2 subgroups. Serum resistin levels in the non-PCOS group were significantly higher than in the PCOS group (p=0.049). Serum resistin levels in the non-PCOS group were inversely correlated to the number of oocytes retrieved (r=-0.386, p=0.039), but no similar correlation was found in the PCOS group. There was no correlation between serum resistin levels and fertility rate or clinical pregnancy rate in either subgroup.'] Is serum resistin level a predictor of ovarian response in in vitro fertilisation cycle?