A digestibility trial was carried out to compare the amino acid (AA) digestibilities of oats and barley. One barley, one winter oat and two spring oat varieties were incorporated into a corn, soybean and maize starch containing basal diet at 20 and 4096 on the expense of starch, and the ileal digestibility of AAs of the diets and cereals determined. The effect of exogenous beta glucanase enzyme on the AA digestibility of experimental diets was also investigated at 409 inclusion rates. To was used as a marker. The comparison of the AA digestibility of the experimental diets showed that the cereal and enzyme effects were amino acid dependent. Neither factor caused significant differences in the digestibility of MIT and HIS. Only the enzyme resulted improvement in the absorption of THR and ILE. while only cereal effect was found in the case of VAL, PHE and LYS. Both factors modified the digestibility of CYS. LEU, ARG and TYR. The interaction between the two factors was not significant in any case. The digestibilities of ILE, LEU. MET of oats were close to the table values (NRC, 1994: EVONIK, 2010), however the measured digestibility of ARG. HIS, LYS and PHE were 6 to 13% lower. In the case of barley, the measured digestibility coefficients of HIS, ILE, LYS, THR and CYs were lower than the table values in most cases.