A simple method for the quantitative analysis of amino [teids [n'eHent ill a protein hydrolysate, or in other mixtures of amino aeids, is deserihocl. The amino aeids are separated on one�dimensional paper chromatogmllls, fOUl" solvent syst;mns being used to resolvo 17 amino acids. The chromatogrums are treatm! with a suitable reagent; to detect the spots corresponding to each amino acid . .!Daeh chromatogram, {,ftcr being made somi�t,mllsparent with dimeth:vlphthalato, is scanned nutomnticnlly, with a densitometer, and the intensity of the light transmitted by the coloured spots is recorded on light-sensitive paper. A straight line relationship was found to hold, [or all amino acids, boi;wcell conccnh'ntioll and log per cent. transmission, Tho most useful range of amino aoid OOllcolltmtion was 2 5 mlYI although tho mothod is usable in tho rango 1-"10 mlVl. 'l'he method includes a nnmber of nOW tOclllli(juOS and tho HYOeage cooflicient of variation for a sillglo readillg for an an1ino n.eid is 5-7 pOl' COllt.