This chapter reviews the literature reporting differences in the incidence of psychosis between migrant and ethnic groups, and discusses methodological issues. Race, culture and ethnicity are three related but distinct concepts. The use of racial categories has largely disappeared from scientific research and been replaced by the use of ethnicity. The chapter builds a model of how migration, culture and ethnicity affect rates of incident psychosis by using the best-researched group, people of African and Caribbean origin in the UK. Social factors are important in the genesis of psychotic disorders. The three most cited possible social reasons for increased rates of psychosis in migrant groups are socioeconomic factors, racism and the urban environment. A sociodevelopmental model would suggest that ongoing negative social experiences, acting on a template of social deprivation and urbanicity, cause changes in social adjustment which predispose to further negative social experiences and which ultimately result in psychosis.