Supernatants from human primary thymic epithelial cell culture were collected. The proliferationpromoting effect of the supernatant on mouse thymocyte, as well as on Tcell line 85, Be 13, HDMar, Peer, Loucy, Molt4, Reh and Jurkat, were observed. The results demonstrated that the supernatants could increase spontaneous 3 HTdR intake of mouse thymocyte, promote ConAinduced thymocyte proliferation and stimulate the proliferation of 85 cell or the cells of HDMar, Loucy and Jurkat at stationary phase, but did not display any effect on Be13, Peer, Molt4 and Reh cells.