We have studied the lipid peroxidation product (malondiadehyde-MDA) levels after thiobarbituric acid reaction, spectrophotometrically and by a high-performance liquid chromatography (HPLC) with UV detection in seminal plasma as well as in the cell fraction. Semen samples were obtained from healthy volunteers and infertile males. Ejaculates were previously classified into studied subgroups according to standard andrological criteria (sperm number, motility, morphology) and defined as: normozoospermia (K), azoospermia (Az), teratozoospermia (T), asthenoteratozoospermia (AT), oligoasthenoteratozoospermia (OAT) and idiopathic infertility (NIF). MDA is a good marker for lipid peroxidation. There were found elevated MDA concentrations (determined by HPLC) in seminal plasma of the all analysed pathological semen samples, especially in patients with OAT. The more pronounced differences between healthy controls and NIF patients were observed in intracellular compartment. The lipid peroxidation of rich in unsaturated fatty acids sperm membranes is considered to be one of the most important effects from ROS-induced cell damage what may lead to persistent infertility.