ABSTRACTDifferent portions of a protein isolate from bovine lungs were exhaustively defatted by solvents of varying polarities. Phospholipids, cholesterol and cholesterol esters, free fatty acids, mono‐, di‐ and triacylglycerols were quantitatively determined in the extracts. Their amount was dependant on the polarity of the solvent employed. Neutral lipids were quantitatively removed by all solvents whereas the amount of phospholipids extracted increased with solvent polarity. The water monolayer capacity of the defatted protein (obtained by the BET equation) showed an increase up to the maximum with the increase of the residual lipid content (determined by Folch wash). The results indicated that more protein polar sites were exposed when the lipid fraction (mainly phospholipids) was pres