This investigation was carried out to study the inheritance of total protein content and amino acid lysine in the three crosses (NM 5612 x NM 5272), (NM 5612 x G. 15) and (NM 5272 x G. 15) of grain sorghum. Potence ratio exhibi ted over-dominance to the lower protein in the two crosses (NM 5612 x NM 5272) and (NM 5272 x G. ·15) and to the higher lysine in the later cross. Partial dominance was observed to the higher protein in the cross (NM 5612 x G. 15) and to the higher lysine content in the cross (NM 5612 x G. 15). Mid parents heterosis for protein content in the cross (NM 5612 x G. 15) exhibited insignificant positive value. Meanwhile mid and better parents heterosis showed highly significant negative values in the other two crosses. Lysine content showed heterosis with highly significant positive values in the cross (NM 5272 x G.15) and negative value in the two other crosses. Broad sense heritability for protein ranged from 34% to 98%, while for lysine was less than 40% in all crosses studied. Number of genes for protein content ranged from one to three pairs, while for lysine was one pair, iH ':h dominance gene effect for both characters. Correlation studies indicate that lysine content is not at all correlated with
protein content, which means that both characters are genetically conditioned by different genes.