A review. An attempt is made to decouple the effects that occur when different electrolytes are added to proteins, esp. enzymes, in buffer solns. In particular, direct mol. 'chem.' interactions between ions and specific sites on the enzyme are distinguished from 'phys.' interactions due to electrostatic and dispersion forces. The latter are often related to a Hofmeister series. It is shown that bulk effects, usually on the pH via a shift of the buffer equil., must be sepd. from direct enzyme-ion interactions. ABTS oxidn. with horseradish peroxidase is taken as an example to show how this sepn. can be done. The different concn. ranges in which these phenomena occur are also discussed. Finally, the influence of ions on a particular enzyme, the NADH oxidase, is compared to their influence on mixed catanionic micelles. The striking similarities can be assocd. with the structure-making and -breaking behavior of the ions and a balanced effect for 'neutral' Hofmeister ions.