The interaction of human hemoglobin with several organic solvents and metal cation has been studied in order to obtain selective precipitation of hemoglobin from solution. Alcohols, and preferably the mixture ethanol: butanol added to a final concentration of 8% (v/v) 1-butanol was found to be superior in this respect, giving close to selective precipitation of hemoglobin from whole blood lysates. An equally specific precipitation was achieved by using zinc-chloride in 10-15 molar excess to hemoglobin. Contrary to organic solvents, complex formation with Zn2+ resulted in a reversible precipitation enabling renaturation using strong chelating agents. Specificity of the hemoglobin-precipitating agents was verified by chromatographic and electrophoretic studies. Applications of the presented methods in analytical chemistry and in the isolation and purification of blood proteins are discussed.