Abstract: The diploid type of Paragonimus westermani in Heilongjiang Province and triploid type of P.westermani in Liaoning Province were examined for amino acids by high performance liquid chromatography (HPLC).Eleven kinds of amino-acids of diploid type and 15 kinds of triploid type were found in metacercaria; 15 kinds amino acids of diploid type and 16 kinds of triploid type were detected in larvae.The amino acids were more abundant in larvae than in metacercaria and more in the triploid than in the diploid type.The predominant amino acids were cystine and Rlutamic acid.