This introductory chapter deals mainly with the principles underlying medical assessment of fitness for work, contacts between medical practitioners and the workplace, and confidentiality of medical information. Medical fitness is relevant where illnesses or injuries reduce performance, or affect health and safety in the workplace. It may also be specifically relevant to certain onerous or hazardous tasks for which medical standards exist. Medical fitness should always be judged in relation to the work, and not simply the pension scheme. It has limited relevance in most employment situations: many medical conditions, and virtually all minor health problems, have minimal implications for work and should not debar from employment. Medical fitness for employment is not an end in itself. It must be maintained.