Selection for increased body weight at harvest in Nile tilapia (Oreochromis niloticus) was carried out for five generations from 1991 to 1996, as a part of the project Genetic Improvement of Farmed Tilapias (GIFT). The base population for selection was composed of a mixture of various three- and four-way cross individuals descending from four wild African strains and four farmed Asian strains. In this paper the procedures used and the results obtained during the first five generations of selection for increased body weight at harvest in the GIFT project are documented, and the impact of the GIFT strain and technology is reviewed.