Oxidative stress and trace elements in the oocytes environment is explored in endometriosis and impact on in vitro fertilization (IVF) outcome assessed. Follicular fluid was aspirated at the time of oocyte retrieval from endometriosis (n=200) and tubal infertility (n=140) and the analytes measured using spectroscopy and HPLC. Increased concentration of reactive oxygen species (ROS), nitric oxide (NO), lipid peroxidation (LPO), iron, lead, cadmium and reduced levels of total antioxidant capacity (TAC), superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), glutathione reductase (GR), vitamins A, C, E, copper, zinc and selenium was observed compared to tubal infertility. Increased ROS and NO in endometriosis and tubal infertility associated with poor oocytes and embryo quality. Increased levels of ROS, NO, LPO, cadmium and lead were observed in women who did not become pregnant compared to women who did. Intrafollicular zinc levels were higher in women with endometriosis who subsequently became pregnant following IVF.