Abstract: X-linked nonspecific mental retardation (MRX) related genes are a group of extensively studied genes whose mutation or deletion results in simple phenotypes of generalized or specific cognitive impairment in patients, such as, low intelligence and poor social adaptability. Studying the biological and cognitive functions of MRX related genes means much not only to the discovery of the genetic basis for non-specific MR, but also to the exploration into a new field of research about the molecular basis of human cognitive function. This paper summarizes recent progress on MRX studies, the current status and the prospect of this field.