Four extruded diets, differing in grain supplementation, were fed to triplicate groups of Atlantic salmon (Salmo salar, L.) with a mean weight of 0.5 kg in a digestibility trial. The diets contained 100 or 150 g kg−1 of precooked rye or wheat, replacing fish meal. There were no significant differences in apparent digestibility coefficients (ADC) of protein, fat or starch which could be related to dietary carbohydrate source or inclusion level. The ADC of dry matter and energy were higher for the diets with wheat than for those with rye, and higher for the diets with wheat than for those with rye, and higher for the diets with 100 g precooked grain kg−1 than for those with 150 g kg−1. The mean ADC of starch was 52% for rye, and 53% for wheat.