The study was performed to estimate the influence of fertilization with Sulphur and Potassium on the range and direction of changes in the content of different forms of nitrogen (Ntot., Nprot., N-NO3, N-NH4) in spring barley. The research was based on the chemical analysis of plant material taken from the strict pot experiments. The experiments were carried out in years 2001-2002 on the soil material of granulometric composition of loam silt. The soil used for investigation was characterized with low content of available forms of Phosphorus, Potassium, Magnesium and Sulphur. The obtained results indicate that fertilization of plants with Sulphur and Potassium had a beneficial effect on the nitrogen metabolism. It was connected with more effective transformation of Nitrogen compounds into proteins in barley from the series fertilized with Sulphur and Potassium in comparison with the values obtained from plants from control objects. As a consequence, the plants fertilized with Potassium and Sulphur in flowering phase were also characterized with noticeably lower contents of mineral Nitrogen (N-NO3, N-NH4).