Schizophrenia is characterized by profound disturbances of cognition, emotion and social functioning. It carries a lifetime risk within the general population of approximately 1%. Genetic epidemiological studies have shown that the syndrome has a high heritability, indicating a significant genetic component to its aetiology. However, the undoubted complexity and probable heterogeneity of the disorder continue to confound research, and the precise underlying neurobiological mechanisms remain largely unknown. Although molecular-genetic approaches face formidable difficulties, the identification of susceptibility genes is likely to provide valuable insights into the aetiology and pathogenesis that could lead to the development of more effective treatments.