A monoclonal antibody BMU7-17 which recognizes an antigenic site unique to the cyanogen bromide fragment, CB2 (residues 56 through 133) of the gamma-chain of human hemoglobin has been produced using cell hybridization techniques. The antibody does not crossreact with hemoglobin A, the isolated alpha- or beta-chains, or with hemoglobin of various mammals. Affinity chromatography on Staphylococcal protein A-Sepharose 4B and radial immuno-diffusion revealed the antibody to be of the mouse IgG 1 class. BMU7-17 identifies F cells in adult and in cord blood specimens, as demonstrated by an indirect immunofluorescence assay. The dissociation constant of the antibody as determined using tritiated hemoglobin F with a double antibody radioimmunoassay has a Kd = 1.2 X 10(-9) moles by Scatchard plot analysis.