SummaryThe transferrin receptor (TFR) has been detected in tissues eharacterised by a high degree of proliferation. We have developed a procedure for isolating TFR from human placental tissues by affinity chromatography on transferrinSepharose. Using gel filtration and electrophoresis in 7% PAAG, it has been shown that the molecular mass of the protein is 180 kDa. The protein has a subunit structure and is made up of two identical subunits, 90 kDa each. The constant for the protein binding to transferrin is equal to 5 x 10 .9 M. The yield of the protein isolated by the novel procedure exceeds 5-fold that obtained by previously described methods.