The recent interest of the food industry in the high‐pressure processing of food materials as an alternative or in addition to temperature treatment requires fundamental studies on the pressure‐temperature behavior of macromolecular food constituents such as proteins. In this paper we review some basic knowledge on the effects of high pressure on proteins. These effects are reversible or nonre‐versible and include changes in intra‐ or intermolecular interactions (noncovalent bonds), in conformation and in solvation. In general, reversible effects are observed below 1–2 kbar (e.g., dissociation of polymeric structures into subunits). Above 2 kbar, nonreversible effects may include complete inactivation of enzymes and denaturation of proteins (unfolding of monomeric proteins, aggregation, and gelation phenomena). Particular attention is directed to pressure denaturation, a complex phenomenon depending on protein structure, on pressure range, and on other external parameters, for example, temperature, pH, and solvent composition (presence of sugars, salts, and other additives).