A new beta-chain hemoglobin variant, Hb Randwick [beta 15(A12)Trp----Gly] was detected in a 43-year-old female of Northern Italian parentage. During investigation for possible diabetes, mild red cell changes were noted and hemoglobin electrophoresis studies were requested. Independently, her sister's assessment had resulted in similar investigations. The most prominent findings were numerous "Hb H"-like inclusions and a positive isopropanol stability test. The hemoglobin variant separated poorly towards the anode at pH 9.2 and the level was estimated to be between 48-50% of the total hemoglobin. The variant beta-chain was partially purified by column chromatography, and its tryptic peptides fractionated by high performance liquid chromatography. Amino acid analysis and sequence data indicated that the tryptophan at residue 15 (A12) had been substituted by a glycine residue. Further study has indicated that eight other family members are heterozygous for the variant; they are clinically normal with no evidence of splenomegaly or history of jaundice, although four of them showed a mild reticulocytosis.