Analysis of alpha-thalassemia syndromes in several German families revealed DNA deletion as well as non-deletion forms as the molecular basis for the defects. Thus, the alpha-thalassemia haplotype was identified as the (-alpha)3.7 rightward deletion form, and the region of the putative recombination process generating such a deletion was further characterized. In addition three different alpha(0)-thalassemia haplotypes, (--)MED, (--) > 26, and (alpha alpha)T, could be detected using alpha- and zeta-globin gene-specific probes.