In recent years, the effect of Toxoplasma gondii infection on psychiatric-related aspects has been increasingly recognized. T gondii has a high affinity for brain tissue where tachyzoites may form tissue cysts and persist life long. In recent years, 15 serological surveys about T gondii infection and psychiatric diseases have been carried out in different areas in China. Studies showed that the prevalence of antibodies against T gondii in psychotic patients was much higher than in normal persons; statistically differences were significant. Studies also reported that raising cats or enjoying the habit of eating raw or under cooked meet were potential risk factors for the infection of T gondii. The epidemiological and serological evidence support the hypothesis that some psychiatric diseases such as schizophrenia or mental retardation might be linked to T gondii infection.