Statistics on global fish and shellfish production show that fish farming represents about 15% of the global fish yields and is expected to exceed 20% by the year 2000. Capture fisheries have already reached their maximum sustainable yield, and this why any increase in seafood production can only be achieved through aquaculture. Increased productivity in aquaculture will be achieved through genetic improvement of species by selection breeding and, potentially, gene transfer technology.Fish farming in ponds and dams was known in China 5,000 years ago and in Europe around 1,000 years ago. Trout farming started just before World War I, and salmon pen and cage farming began in Norway in the 1970s. About ten years later, a national breeding program was developed, becoming the starting point of this new activity (Gjedrem et al. 1988). After six generations of selection breeding a Norwegian salmon was produced that was 50% bigger than its ancestors from the Norwegian rivers. Later, the Aquaculture Research Institute (AKVAFORSK) successfully transferred the Norwegian salmon breeding program to tilapia farming in the Philippines and carp farming in India. The history of farmed salmon makes it one of the last species to be domesticated together with a few other cultured fish species, although fish culture as such has been known for thousands of years.Efforts are now underway to domesticate new species for aquaculture and to meet the global demand for increased food production. In order to optimize results in new breeding programs, genetic engineering and genetically modified organisms (GMOs) offer new possibilities. The objectives of this paper are to discuss technical, environmental and management considerations regarding the use of GMOs in aquaculture.