The AFP receptor (rAFP) was discovered in embryonal and tumor tissues with a high level of proliferation. The AFP‐binding protein (AFPbp) possibly containing the AFP‐receptor (rAFP) was isolated from human embryos and human breast cancer tissue using affinity chromatography on an AFP‐Sepharose column. The similarity of molecular weight, subunit composition, and immunological characteristics was shown for embryonal and tumor AFPbp using immunoblotting, gel‐filtration, and PAAG electrophoresis. Judging from Superose‐12 gel‐filtration data, the protein molecular weight made up to 320‐380 kDa. The presence of an IgG‐binding site was detected in embryonal and tumor AFPbp by Western blot analysis.