Cow nasal tissue contains a protein which shows specific binding activity for ‘green’ smelling compounds such as 2‐isobutyl‐3‐methoxypyrazine. This protein has now been purified using anion‐exchange fast protein liquid chromatography. The protein has a relative molecular mass of 400000–44000, s= 3.1 ± 0.3 S, pI = 4.7 ± 0.1 with an absorbance maximum at 278 nm, and consists of two subunits with an identical relative molecular mass of 19000. It is localised in the soluble fraction of cells from the olfactory mucosa and respiratory mucosa from the middle part of the maxillary and nasal turbinates, and is absent from all other tissues tested.