C-terminal amino acid sequence analysis seemed to be established procedure, as the counterpart of Edman's N-terminal sequencing method. However, poor recovery of the C-terminal amino acids in the reaction in homogeneous solution suggested further improvement of the method. In the present study, N-terminal amino acid was fixed covalently to the controlled pore glass (CPG) beads and the C-terminal amino acid was activated (by treating with acetic anhydride), coupled with thiocyanate to form thiohydantoin (TH) ring at the C-terminus. Then, the C-terminal amino acid was split off as the corresponding TH derivative, and analyzed by HPLC. Hydrolysis of the TH derivative was achieved at 60°C in the presence of 2 M HC1 for 2 h. Solid phase fixed peptide was washed simply with acetone, and dried for the next cycle of the reaction. So far obtained results in the heterogeneous mixture are not satisfactory in terms of the recovery of the C-terminal TH, and improvement of the recovery and further steps are under progress.