In Thailand, two types of high 1% A2-B-thalassemia genes:βO-thalassemia (βO-thal) or classicalβ-thalnssemia andβ+-thalassemia (β+-thal) or mild 6-thalasseinin exist. This study presents hematologic data and globin chain synthesis in peripheral blood of the genuineβ+-thal hetcrozygotes in comparision with those of theβO-thal heterozygotes. Thirty individuals of Thai and Chinese exctraction with theβ+-thal heterozygosity were hematologically examined. The hematologic means of hemoglobin concentration, MLV, MCH, MCHC, 11h A2and alkali3denaturation hemoglobin of theβ+-thal traits were, 11.7 g%, 67.8 u3, 21.5γγ, 32.1%, 4.94% and 1.20% respectively. These were not statistically different from those of theβO-thal traits of our previous study(1). The globin chin synthesis in reticulocytes were performed by incorporation of3H-Leucine for 3 hours. The mean of total radioactivityα/βratio in 11 normal controls was 1.07±SD 0.03 The mean ofα/βratio in 9β+-thal traits was 2.03±SD 0.10 which was significantly different from that in 7βO-thal traits of 2.28±SD 0.07 Our globin chain synthesis thus appears to be helpful of discriminating theβ+-thal trait from theβO-thal trait.