The aim of this study was to determine and compare the level of ROS in seminal plasma and other sperm parameters (count, morphology, membrane integrity, maturity, DNA-fragmentation) in order to find out the relationship between ROS concentration and spermatozoa quality and their effect on fertilization and pregnancy of patients who became pregnant and those who did not after IVF/ICSI treatment. 26 IVF and 22 ICSI patients were included in this study, the ROS level in seminal plasma and sperm concentration, vitality (Eosin-test), motility, morphology, membrane integrity (HOS-test), maturity (Chromomycine CMA3) and DNA Fragmentation (TUNEL) results and their relationship to fertilization and pregnancy were analysed. ROS concentrations were at the same level in the seminal plasma of male partner of patients who became pregnant and those who did not. The other semen parameters, concentration, motility, vitality, membrane and DNA integrity were similar in both groups. However, in both groups a negative correlation could be found between ROS concentration and sperm vitality, membrane integrity and morphology. Besides an inverse correlation, could be found between TUNEL, vitality, and membrane integrity. In Conclusions: ROS concentration in seminal plasma affects spermatozoa’s quality but can not affect the fertilization rate in IVF/ICSI programme.