Radioactive markers in ion exchange chromatography of amino acid mixtures of biological samples is one of several methods used to identify a particular amino acid. It is shown that in fractions of column effluents-C14-labeled amino acids can be detected relatively easily and economically by liquid scintillation or gas flow systems. The interference of the small quantity of labeled amino acid required to give a significant counting rate with the color yield of the amino acids under investigation has been shown to be negligible.