Aquaculture in developing countries is largely based on unimproved fish strains. There is ample evidence indicating the potential of genetic improvement programs and a range of selection methods may be used. Examples of the application of mass, cohort, within family, and combined between-within family are given.The methods are discussed in terms of their effectiveness and suitability. It is concluded that in principle most of the methods can work well, provided the selection program is started with a population with a broad genetic base and that during its conduct a balance is struck between selection intensity and containment of inbreeding. Programs that entail the collection of very detailed information are more suitable for national research organisations, whereas simpler ones may have greater appeal to commercial operators.