An experiment in nutrient solution was carried out to study the effects of increasing levels of N on growth, yield and mineral composition of 5 cultivars of grain sorghum namely: TE Y 101, C 101, C 102, P 8417, and E 57. Four levels of N were used, all of them being a fraction of the concentration given in the solution of HOAGLAND & ARNON (1950) nº 1. Differential responses in dry matter, yield and N, P and K contents were observed and discussed.