The establishment of the AMI services in 1926 not only changed colonial health paradigms in Angola: it also had a considerable impact on colonial knowledge and debates about the demography of Angola’s ‘native’ population. Driven by persistent fears of depopulation and profound dissatisfaction with existing demographic data, medical doctors used the new AMI framework to probe novel methods of data gathering and analysis. This chapter illuminates the emergence, development and consequences of this ‘medical demography’, as I term the demographic endeavours of colonial doctors. It analyses how, during the interwar years, colonial practices of hygiene and demography became closely intertwined; how medical demography generated new insights into Angola’s population dynamics; and how it played an important role in ongoing debates about the presumed decrease of the colony’s ‘native’ population as well as the ‘racial’ specificities of African population trends.