Morphine addiction has become a long-time, serious medical and social problem. To understand the cellular mechanisms of morphine application and addiction, the effects of chronic morphine treatments were examined in primary cultured human neurons. Our results show that, surprisingly, morphine protects cultured human neurons against serum deprivation and staurosporine induced cytotoxicity. Morphine downregulates proapoptotic factor Bax levels in cultured human neurons. In addition, heat shock protein 70 is also involved in morphine protection. Our data suggest that chronic morphine application may be beneficial to stimulate cell survival.