Influence of nine synthetic peptides from the C-terminal part of human α-2 interferon (EN) molecule on growth of a human T-lymphoblastoid cell line MT-4 was investigated. It was shown that some peptides inhibited the proliferation of MT-4 cells. It was also found that MT-4 cells expressed specific receptors on the outer surface of the plasma membrane. All studied peptides competed for binding to a common binding site. Antiproliferative activity of the peptides correlated with their length and affinity to receptors on the outer membrane of MT-4 cells.