This paper present that preparations of M. vaccea, which included suspensions of live bacilli, irradiation-killed bacilli and high temperature killed bacilli, for the effect on lymphocyte proliferative response of peripheral blood in healthy persons were compared by 3H-TdR incorporation method. CPM of control was 448 +/- 131, CPM adding suspensions of live M. vaccea, irradiation-killed bacilli and high temperature killed bacilli were 1037 +/- 194, 2299 +/- 140, 1819 +/- 528, 994 +/- 186, respectively. Stimulative index of all four preparations were more than 2.0, specially suspensions of live and irradiation killed M. vaccea is more effective than BCG and high temperature killed M. vaccea, which were 5.13, 4.06, respectively. In another experiment, suspensions of live, irradiation-killed and high temperature killed M. vaccea plus rIL-2 were found more effective than rIL-2 alone. CPM of them were 9544 +/- 1727, 8530 +/- 714, 8230 +/- 1035, and 3721 +/- 1336, respectively, but BCG was 6904 +/- 1218. The results show that preparations of M. vaccea tested have distinctly promotive effect for proliferative response of lymphocyte in vitro. The addition of rIL-2 to suspendions of live M. vaccea, irradiation killed and high temperature killed M. vaccea cooperatively increased the effects of proliferative response mentioned above.