In order to determine the prevalence of thalassemia and hemoglobinopathies in different regions of northeast (NE) Thailand and Vientiane, Laos People's Democratic Republic (PDR), a total of 1,809 blood samples were collected consecutively from individuals attending antenatal care services at 11 community hospitals in different regions of NE Thailand and three hospitals in Vientiane, Laos PDR, from May 2009 to April 2010. All individuals were investigated for thalassemia and hemoglobinopathies using standard methods. For individuals from NE Thailand, the carrier frequencies were 41.7% for Hb E [beta 26(B8) Glu -> Lys, GAG>AAG], 5.8% for alpha(0)-thalassemia (alpha(0)-thal), and 0.9% for beta-thal. The THAI deletion type of alpha(0)-thal was found in one individual from an ethnic minority. From a group of pregnant Laotian women, 30.1% were Hb E carriers. The prevalence of alpha(0)-thal of 8.6% for the Laotian women was similar to that found in the upper northeastern part of Thailand. The frequency of beta-thal was 2.3 %. The proportion of carriers of alpha(+)-thal and Hb Constant Spring (Hb CS, alpha 142, Term -> Gln (TAA>CAA in alpha 2)]) from Thailand and Laos was significantly different. The frequency of Hb Pakse [alpha 142, Term -> Tyr (TAA>TAT in alpha 2)] was relatively low for Thailand as well as for Laos. The results indicate that thalassemia and hemoglobinopathies are a significant health burden in the region and that a prevention and control program for severe thalassemia diseases should be established in Laos.