The goal of performed investigations was estimation of magnetic field, chemomutagen and gamma rays influence on the level of biological injuries of M1 barley plants, expressed by variation of yield structure parameters. Generally in both variants of the experiment, stationary and alternate magnetic field induced the biostimulation effect of analyzed traits as compared to control plants. The results obtained depended on the type of magnetic field used, their intensity, doses of gamma rays or chemomutagen and kind of analyzed trait. In contrast to the magnetic field, the doses of MNU used and particularly the gamma rays caused strong reduction of yields parameters. The reduction observed increased with the use of higher doses of irradiation and MNU treatment. In common treatments (magnetic field + gamma rays or magnetic field + MNU) the values of yield structures obtained were lower as for the separate use of magnetic fields but higher than for separate treatment of grains with gamma rays or MNU. This indicates the protected influence of magnetic fields on the level of biological injuries induced by mutagenic treatment of grains with gamma rays or MNU. This effect has undoubtedly a connection with the biostimulate influence of the magnetic field on the value of yield structure parameters.