AbstractA widespread practice is to use free energies of transfer between organic solvents and water (ΔGtransfer°) to define hydrophobicity scales for the amino acid side chains. A comparison of four ΔGtransfer° scales reveals that the values for hydrogen‐bonding side chains are highly dependent on the non‐aqueous environment. This property of polar side chains violates the assumptions underlying the paradigm of equating ΔGtransfer° with hydrophobicity or even with a generic solvation energy that is directly relevant to protein stability and ligand binding energetics. This simple regaining of the original concept of hydrophobicity reveals a flaw in approaches that use ΔGtransfer° values to derive generic estimates of the energetics of the burial of polar groups, and allows the introduction of a “pure” hydrophobicity scale for the amino acid residues.