Electronic instruments should be immune to electromagnetic interference (e.m.i.) but must also be easy to use and service; the designer needs to resolve problems of conflicting interest. Several basic approaches to the e.m.i. problem are identified and practical ways of applying them are considered. Also discussed are the usefulness of Superscreened joints and cables, the importance of correct installation of connectors, and the need to reject unplated aluminium as a screening material. Two examples of e.m.i. immune instrument designs are examined with emphasis on practicality.