Free amino acid contained in the smoke of seven different cigarettes, respectively made from a single variety of tobacco, have been quantitatively determined by paper chromatography and colorimetry. Fourteen amino acids (α-alanine, proline, glycine, glutamic acid, glutamine, β-alanine, serine, γ-amino butyric acid, aspartic acid, valine, leucine, ornithine, threonine, and phenylalanine) and three ninhydrin-positive substances were detected. Of these acids α-alanine was most abundant (10.5-268.2γ/1 cigt.) and proline (5.5-25.1γ), glycine (4.7-22.5γ), etc. followed in this order. In general, the smoke of sun-cured or bulk-sweated tobaccos contained more kinds and more amounts of amino acids than that of flue-cured tobaccos. In another experiment, it was found that about 15% of artificially added mono-sodium glutamate is transferred into cigarette smoke.