Opaque -2 maize gave significantly better nett protein utilisation (NPU) values than normal maize varieties in trials performed with rats and chickens. Altogether seven varieties of maize were tested of which three carried the opaque -2 gene and these proved to rank first, second and third in NPU values. In the chicken trial normal white maize supplemented with 0,013% 1-tryptophan and 0,04 %l-lysine was not significantly different to two of the Opaque -2 maize samples. A commercial normal yellow maize fortified with similar levels of these amino acids held a similar position as the fortified N variety, however, supplemented with higher levels of these amino acids (double the former levels), yellow maize was not significantly different to the top Opaque -2 maize variety in the trial.