AIM:To supply the theoretic evidences of elongating the lifetime of neuron-like cells differentiated from adult rat mesenchymal stem cells, we investigated the relationship between the differentiation and apoptosis in the process of induction. METHODS: The mesenchymal stem cells(MSCs) were isolated primarily from rat bone marrow, and purified by passage culture. The 5th passage of MSCs was induced by ?-mercaptoethanol and all-trans-retinoic acid (ATRA). After 1 h, 3 h and 5 h of induction, the cells were stained immunocytochemically with anti-MAP-2 and anti-GFAP antibodies, respectively. In addition to counting the ratio of neuron-like cells in MSCs, DAPI staining was employed to identify whether the differentiated cells have an apoptotic morphological changes. The ratio of apoptotic cells at 1 h, 3 h and 5 h after induction were detected by flow cytometry (FCM). RESULTS:Neuron-like cells appeared among MSCs and could be identified by MAP-2 staining 30 min after MSCs being treated by ?-mercaptoethanol and ATRA. However, 5 h after induction, some of these neuron-like cells began to float and die. With DAPI staining, the nuclei of some dying cells were shown to be condensed and later fragmented. The ratios of cells undergoing apoptosis at 1 h,3 h and 5 h after induction by ?-mercaptoethanol and ATRA were 1.5%?6.1%?21.5% and 1.5%?1.7%?12.3%, respectively . CONCLUSIONS:1. ?-mercaptoethanol and ATRA had the different ability that induced MSCs to differentiate to neuron-like cells. 2. Apoptosis was also initiated in the process of differentiation, and there is positive correlation between the ratio of differentiation and apoptosis.