AbstractSedimentation velocity analyses of the isolated subunits of mouse 7S nerve growth factor (NGF) and their binary complexes have been performed. The 2.5S (β) form of NGF binds 2 α subunits independent of the presence of γ subunits. Two γ subunits are also complexed by 2.5S NGF; however, this interaction is dependent on the presence of a carboxyl terminal arginine residue on the β polypeptide chain. The partial loss of this residue in 2.5S NGF preparations results in a ternary complex(es) with a reduced sedimentation coefficient(s). The two binary complexes formed (α2‐β and β‐γ2) show markedly different pH stability profiles. The α and γ subunits do not form a demonstrable complex, but apparently can interact in the ternary complex to render it more stable than the sum of the α‐β an