A comprehensive overview and analysis of mortality and health patterns and differentials of immigrants and their descendants in Belgium is conducted. Belgium is a diverse population consisting of many nationalities with long migration histories to this country. The authors distinguish between two clearly defined groups in the Belgian population: the migrants by country of origin, and their children born in Belgium by country of origin of the parents, regardless of the nationality at birth or the nationality acquired. The findings based on this analysis suggest that the general pattern of mortality by age and by cause of death strongly underscores the need to move behind mono-causal explanations of differentials in mortality by migrant population, ethnic background or nationality of origin. There does not seem to be a single factor that explains a migrant or ethnic mortality advantage in Belgium. Notwithstanding the migrant health effect, many factors contribute over the life course to the final result in life expectancy, sometimes in a positive, sometimes in a negative direction.