We report a Thai family in which five members are Hb G-Makassar heterozygotes and one member is, in addition, a heterozygote for β0-thalassemia (IVS-I-1, G → T). We confirm that the previously presumed mutation at codon 6 of the β-globin gene is GAG → GCG. Hb G-Makassar heterozygotes are asymptomatic and hematologically normal. The Hb G-Makassar/β0-thalassemia compound heterozygote has features of thalassemia minor. A simple and rapid polymerase chain reaction-restriction fragment length polymorphism for the detection of Hb G-Makassar is described.