In vitro globin chain synthesis ratios (beta/alpha) were determined using high performance liquid chromatography (HPLC) in twenty-five alpha or beta-thalassemiaes as well as six normal controls. Among thalassemiaes nineteen were Japanese and six Korean. Two kinds of cation exchange columns.; Mono S, HR 5/5 by Pharmacia and TSK gel by Tohso were compared. Hemolysates (10%), in stead of purified globin peptides, were directly subjected to the both columns, and 3H-labeled globin chain in vitro synthesized were separated on them. The Tohso column gave better resolution of globin peptides, resulting in sharp elution profiles. The HPLC system took about two hours for an analysis of a sample. In contrast, the conventional carboxymethyl cellulose (CMC) chromatography by Clegg need larger sample amounts for globin extraction and twenty-four hours to be completed. The HPLC is evidently simple and rapid. The globin chain ratios thus obtained by HPLC were 1.04-1.08, 0.23-0.89, 1.22-1.62 and 2.05-4.29 for normals, thirteen beta-thalassemia minors, seven alpha-thalassemia traits and three Hb H diseases respectively.