Nephrotic Syndrome (NS) is a disease in which immune system function disorders play an important role. The aim of the study was an assessment of intracellular expression of cytokines in primary NS including assessment of intracellular expression of monokines (TNF-alpha, IL-8) in non-specific LPS stimulation system and intracellular expression of lymphokines (IL-2, INF-gamma, IL-4, IL-6) in experimental system with application of stimulation with ionomycin and PMA. The study included 47 children with NS aged 2-16 years. After activation of whole blood cells in the presence of brefeldin A the cells were labelled with monoclonal antibodies against surface antigens. In the second phase the cells underwent permeabilisation and were labelled with monoclonal antibodies against individual cytokines. The studies performed demonstrated in children with NS relapse an increase of intracellular synthesis of cytokines characteristic of Th1 system (IL-2) and a decrease of synthesis of cytokines characteristic of Th2 system (IL-4, IL-6). In these patients an increase was also found of intracellular synthesis of proinflammatory monokines (TNF-alpha and IL-8). The studies performed, confirmed the earlier observations concerning abnormal cellular response in NS and demonstrated that differences in serum concentrations of individual cytokines may result from disturbances in their intracellular synthesis.