Blood counts, hemoglobin (Hb) high performance liquid chromatography (HPLC), and DNA analyses were performed on 260 children, aged 5 months to 16 years, at Siem Reap to assess the prevalence of thalassemia and other hemoglobinopathies in regional Cambodia. Hemoglobinopathies were present in 134 children (51.5%) with 20 abnormal genotypes identified. α-Thalassemia (thal) (35.4%) was the most prevalent disorder and the -α3.7 gene deletion was the most common α-globin gene abnormality. The - - SEA deletion and nondeletional forms of α-thal, Hb Constant Spring [Hb CS, α142, Term→Gln, TA→CAA (α2)], Hb Paksé [α142, Term→Tyr, TAA→TAT (α2)] and triplicated α genes, were also present but at low frequencies. Hb E [β26(B8)Glu→Lys, GAG→AAG] (28.8%) was the most common β-globin gene abnormality, whilst β-thal was only detected in two children (0.8% of cases). Although hemoglobinopathies were common, the majority of abnormalities detected (heterozygous -α3.7 and Hb E) were not clinically significant. On the basis of these findings, and with the majority of abnormalities being mild, it seems improbable that thalassemia represents a major health burden in this region of Cambodia.