Hemoglobin (Hb) Ottawa [α15 (A13) Gly→Arg], also known as Hb Siam, was first described in an 82-year-old Canadian in 1974. The same year, a second case was reported in a 28-year-old Chinese male living in Thailand. A third case was found in 1986 in a Chinese female living in the Hubei province of China. Since then, there have been no reports of Hb Ottawa in mainland China in the English literature. Hb Ottawa results from a GGT→CGT mutation in codon 15 of the α1 or α2-globin gene. Hb Ottawa carriers do not present any clinical symptoms or hematological changes, and are often diagnosed during a health examination and thalassemia screening. In a hemoglobin survey of 9745 students in Chaozhou, Guangdong, China, we identified four cases of Hb Ottawa in a thalassemia screening by Hb electrophoresis, and confirmed it to be the result of a GGT→CGT mutation in codon 15 of the α2-globin gene by DNA sequence analysis.