We describe a new alpha 2-globin gene point mutation found in six individuals of a three-generation Dutch family. The mutant, which is associated with a mild alpha-thalassaemic phenotype, is not detectable at the protein level. The alpha 2 cd129 (CTG-->CCG) transition was found by molecular analysis using denaturing gradient gel electrophoresis (DGGE) and single-strand conformation analysis (SSCA) followed by direct sequencing of the alpha 2-globin gene. Southern analysis revealed a triplication of the zeta-gene in cis with the mutant alpha-globin gene.