We have identified three types of α-thalassemia in 28 members of an Indian family from Durban, South Africa. The rare South African (SA) type of α-tha-lassemia-1, which is characterized by an ∼23-kb deletion involving the ψζ, ψα2, ψαl, α2, α1, and θl genes, was present in 13 members [6 simple heterozygotes, 5 with Hb H disease of the ∼(S A)/-α(-3.7 kb) type, and 2 with Hb H disease of the --(SA)/-α(-4.2 kb) type]. Seven others were heterozygotes for α-thalassemia-2 (-3.7 kb), 1 was homozygous for this deletion, and 1 was a compound hetero-zygote [-α(-3.7 kb/-α(-4.2 kb)]. Hematological and hemoglobin composition data indicated a moderate anemia in all 7 patients with Hb H disease with severe microcytosis and hypochromia, no elevation of γ-chain synthesis, low levels of Hb A2 (0.3-0.7%), and low levels of Hb H. The most severe disease was present in 2 teenagers with the --(SA)/-α