AbstractThe nerve growth factor protein (NGF) isolated from mouse submaxillary gland has been shown to be necessary to the development of vertebrate sensory and sympathetic ganglia. Also, wide ranging alterations in the levels of NGF in the peripheral circulation of humans suffering from a variety of neuropathies have been reported. Many of these reports relied on the use of antibodies directed to the mouse β‐NGF subunit for their quantitation of human NGF antigen. We report here on the lack of crossreaction between antibodies directed to mouse β‐NGF and its human counterpart isolated from placenta at