In the last 50 years a significant decrease in human fertility has been observed. The result of research indicate that 6% of men aged 15-44 years are infertile or their fertility is significantly compromised. It has also been stated that 15% of couples have fertility problems. Among infertile couples it is a man who is responsible for 50% cases of infertility. Test results show that hormonal disturbances and abnormalities in semen production belong to main causes of infertility, while anatomic anomalie can be responsible for infertility only in few cases. Various chemical substances which appear in the environment may disturb fertility of men. Polluted soil, water and air are the sources of constant exposure to xenobiotics. Substances disturbing hormonal balance (endocrine disruptors) such as pesticide, dioxins and organic solvents cause the highest danger. Improper work conditions such as too high temperature, radiation, exposure to harmful substances also have negative influence on reproductive abilities of men. In addition, it has been noticed that both, some drugs and past infections of reproductive system may have a negative impact on fertility. Studies carried out in recent years have proven that improper lifestyle such as inadequate diet, alcohol abuse, smoking and long-term stress exposure can be the reason for fertility distrurbances in men. The latest findings have stressed genetic factors which may influence reproductive abilities of men.