The "in vitro" effect of different concentrations of polyclonal human immunoglobulins for intravenous use (IVIG) on cultured T-lymphocyte response to phytohemagglutinin (PHA) was evaluated. Four dilutions of IVIG corresponding with the "in vitro" doses currently employed in therapy have been tested by the effect on PHA stimulated cultures. The dilution of IVIG corresponding with a low therapeutical dose gives a higher statistically significant stimulating effect. The results obtained in our work agree with previous studies performed on activated B-cells. We can suppose the immunoglobulins may control the T-lymphocyte activation either by a direct link with a specific Fc-receptor expressed on the surface of activated T-cell or by affecting the cytokines release from monocyte cells.