Abstract.  Neuropathy target esterase (NTE), the human homologue of a protein required for brain development in Drosophila, is expressed primarily in neural cells but is also detected in non‐neural cells. Although NTE has been proposed to play a role in neurite outgrowth and process elongation during neurodifferentiation, the function of NTE has not been defined in neural cells. In this study we have investigated the possible role of NTE in neuroblastoma cells and non‐neural cells using an over‐expression strategy. Over‐expression of NTE in human neuroblastoma SH‐SY5Y cells and monkey kidney COS7 cells led to an accumulation of NTE on the cytoplasmic surface of the endoplasmic reticulum and inhibition of cell proliferation. In particular, high levels of NTE arrested COS7 cells at G2/M stage yet was not associated with arrest at a particular phase of the cell cycle in SH‐SY5Y cells. Moreover, over‐expression of NTE did not induce apoptosis in two kinds of cell lines as assessed by flow cytometry. These results suggest that the role of NTE over‐expression in cell proliferation is associated with different mechanisms in different cells.