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To investigate the effect of S-nitrosoglutathione (GSNO), a nitric oxide donor, on platelet production from megakaryocytesdifferentiated from cord blood CD34+ cells in vitro, the CD34+ cells from eight fresh umbilical cord blood samples by a high-gradientmagnetic cell sorting (MACS) system were cultured in serum-free medium for 14 d with thrombopoietin (TPO) 50 ng/ml, IL-3 10 ng/ml,stem cell factor (SCF) 50 ng/ml and rHuGM-CSF 20 ng/ml. Then, CD61+ cells were purified by MACS system from these CD34+ cells,and were cultured in serum-free medium supplemented with TPO 50 ng/ml, IL-3 10 ng/ml and SCF 50 ng/ml in the presence (treatmentgroup) and absence (control group) of GSNO for 30 min or 2 h. Platelet-sized particles were counted by flow cytometry; megakaryocytestructure was detected by scanning electron microscope. Aggregation of the thrombin-induced platelet particle was observed underinversion microscope. cGMP was assessed by commercial ELISA kit. The results showed that, compared with the control group, thenumber of platelet-sized particles significantly increased (P<0.05) in the treatment group, in which megakaryocytes presented significantpseudopod formation and extensive membrane blebbing. The platelet particle aggregation could be observed under microscope afterthrombin induction. cGMP activity was significantly increased after treatment with GSNO (P<0.05). These results propose that GSNOcan facilitate platelet production from megakaryocyte, and it may be partly through cGMP pathway.