Amino acid analysis by precolumn derivatization with phenyl isothiocyanate and subsequent characterization of the phenylthiocarbamyl derivatives by high-performance liquid chromatography on an inexpensive Supersphere C8 column is described. The phenylthiocarbamyl derivatives of common amino acids from protein hydrolysates are separated within 15 min. Suggestions for optimization of the system with respect to the separation of closely eluting derivatives are given. The characterization of side-chain-derivatized, e.g., phosphorylated and sulphated amino acids and of a series of biologically active amino acid analogues is described.