A silent hemoglobin variant with substitution of serine for glycine at position 69 of the 6-chain was discovered in a healthy individual. Reverse-phase HPLC was used for globin chain separation and to separate the tryptic peptides of the variant. This variant was undetectable by conventional methods of protein separation such as electrophoresis, iso-electric focusing, and ion-exchange chromatography. This observation demonstrates the potential of reverse-phase HPLC as a tool for the search and detection of neutral substitutions in variants of hemoglobin and other proteins, and its usefulness for screening genetic variations in human populations.