There are little data on the properties of ion channels in the inner nuclear membrane of lymphocytes, though the transport system between cytoplasm and karyoplasm is of a great importance for a complex genetic regulation in these cells. Using the patch-clamp technique we have investigated ion channels of the inner membrane of nuclei isolated from cultured T-lymphoblasts. Our research has shown that there are anionic (370 pS) and cationic (152 pS) channels on the inner nuclear membrane. The latter were characterized by fast kinetics and rapid fluctuations; they had high open probability and were inactivated at large negative potentials. These channels were permeable for K+ and Na+, but impermeable for Cl-. The physiological role of the channels is not clear, but they may play an important role in the ion balance between the cytoplasm and the lumen of the endoplasmatic reticulume of the cell.