As a start some differences between physical and adsorption are emphasised. The distinction between chemical and ionic pumping is defined and discussed, and examples quoted, both recent and historical. Since in getter-ion pumps different kinds of gases have to be handled simultaneously, examples are mentioned where the presence of some gases is known to greatly influence the kinetics of adsorption of other particular gases. In any case, the interpretation of the readings obtained when checking pump performance is hazardous when gases of differing condensation coefficient are present together. A simple test that measurements are well-founded is described. Some surface reactions that can limit the performance of getters, and ways of possible improvement, are suggested.