Preparations of horse heart cytochrome c have been obtained immobilized on Sepharose derivatives via lysine epsilon-amino groups, carboxyl groups of aspartic and glutamic acid residues, methionine and histidine residues as well as imidazole groups additionally introduced by means of modification of free carboxyl groups by histamine. Dissociation constants have been determined for complexes of adrenodoxin, hepatoredoxin , cytochrome b5 heme-containing tryptic fragment and myoglobin with cytochrome c preparations immobilized via lysine residues (cytochrome c-Sepharose I) or additional imidazole groups (cytochrome c-Sepharose II). The latter adsorbent possesses a 2-3 times higher affinity to adrenodoxin and hepatoredoxin than the former. The parameters of interaction with cytochrome c-Sepharose II constitute for the proteins studied the following sequence: adrenodoxin (the highest affinity) greater than or equal to hepatoredoxin greater than cytochrome b4 heme- containing tryptic fragment greater than myoglobin. The efficiency of cytochrome c-Sepharose II application in the course of adrenodoxin, hepatoredoxin and cytochrome b5 purification, as well as isolation of cytochrome b4 heme-containing tryptic fragment has been shown.