The investigations on meat flavor, which was produced on heating, revealed the existence of the precursors in the water soluble fraction of pork extract. This fraction contained mainly carbohydrates and amino acids e.g., valine, glycine and alanine. This suggested that the flavor could be produced by the heat reaction of the amino acids and sugars present. In the model experiments, in which several amino acids were heated with sugars, valine, isoleucine, leucine, lysine and proline showed to give favorable flavor. When valine and glucose were reacted in several conditions, 10 to 11 kinds of carbonyl compounds could be detected as hydrazones by thin-layer chromatography. Isobutyraldehyde was one less carbon aldehyde for valine, which was detected for the principal products originated in valine by thin-layer chromatography, melting point and ultra violet, infrared spectrum. It was considered that isobutyraldehyde was formed by the Strecker reaction of valine and some aromas of roasted meat were also produced by this reaction.