Apoptosis in human acute lymphoblastic leukemia cell line Molt-4 cell and macrophage cell line Ana-1 cell could be induced by fission fragment ¹⁴⁷Pm. The cumulative absorption dose of ¹⁴⁷Pm in cultural cells through different periods were estimated. By using fluorescence microscopy and microautoradiographic tracing it can be found that Molt-4 and Ana-1 cells internally irradiated by ¹⁴⁷Pm, displayed an obvious nuclear fragmentation and a marked pyknosis in immune cell nuclei, as well as DNA chain fragmentation and apoptotic bodies formation. The microautoradiographic study showed that ¹⁴⁷Pm could infiltrate through cell membrane and displayed membrane-seeking condensation in cells. At the same time, the membrane-bounded apoptotic bodies were observed. Experimental results in recent study provide evidence that Molt-4 and Ana-1 immune cells undergo apoptosis while internally irradiated with ¹⁴⁷Pm.