["Obesity's impact on micro-environmental oxidative stress and follicular fluid (FF) viscosity and whether or not it has any effect on in vitro fertilization (IVF) success is a matter of debate.", 'In this study, our aim was to evaluate the levels of oxidative stress markers and the FF viscosity in obese and non-obese patients.', 'Eighty norm-responder patients undergoing IVF were prospectively grouped according to their body mass indexes (BMI). Group 1 (n\xa0=\xa040) and group 2 (n\xa0=\xa040) had BMI values of ≤24.9 and ≥25.0, respectively. Total sulfhydryl (RSH) levels (nmol/m) and the formation of thiobarbituric acid-reactive substances (malondialdehyde, or MDA) (µmol/ml) in FFs were quantified. For the first time in our study, FF viscosity with changing BMI values was also determined.', 'The mean levels of MDA (µmol/ml) and RSH (nmol/ml) were not significantly different between groups (1.37\xa0±\xa00.51; 1.51\xa0±\xa00.51; p\xa0>\xa00.05 for MDA and 0.42\xa0±\xa00.30; 0.41\xa0±\xa00.20; p\xa0>\xa00.05 for RSH, respectively). Similarly, the FF viscosity (centipoise) was not different between groups (1.28\xa0±\xa00.28; 1.30\xa0±\xa00.19; p\xa0<\xa00.05, respectively). Independent of BMI, no correlation was found between FF levels of oxidative markers and the number of oocytes retrieved or the fertilization rates.'] Is obesity a descriptive factor for oxidative stress and viscosity in follicular fluid of in vitro fertilization patients?