Based on the explanation by the IACUC (Institutional Animal Care and Use Committees), environmental enrichment is an environment in which complex stimuli are provided to alleviate the occurrence of abnormal behaviors. Enrichment for primates is a kind of management or treatment for caged primates to provide complex stimuli and thereafter to enhance their psychological well-being. Scientists have studies this topic for many decades. The major concern of this topic is that the primates are very active, curious and intelligent animals and need more complex and enhanced environments to live. If the primates were housed but ignoring their necessity of environmental enrichment, the abnormal behaviors may develop. Most of these abnormal behaviors were referred to "stereotypic behaviors", that is under a condition with bad environmental enrichment, affected animals act in repetitive, invariant patterns and these actions do not have goal or function. The stereotypic behaviors of non-human primates are generally divided into two categories: one is the deprivation, or self-directed behaviors and another is the repetitive locomotion. It is believed that environmental enrichment is an important part - maybe one of the critical parts - in management of primates and may be one of the key points influencing success of the coming SARS virus animal trials.