Three brook trout transferrins, designated A, B and C, were purified by use of rivanol precipitation and gradient elution chromatography with DEAE-Cellulose. Physical and chemical analyses of the purified transferrins demonstrated that each type had at least four sialic acids attached to the protein moiety and that the A type of transferrin has a number of amino acid substitutions, as shown by amino acid analysis and fingerprinting. No differences could be shown between the B and C types. Analyses of molecular weights were inconclusive.