Lessons have to be learnt from the mistakes and oversights for which planners have been responsible as urban populations have escalated during the latter half of the 20th century. For people living in densely populated cities the best possible health can only be achieved if due consideration is given to the creation of a broadly favourable environment. The causes of urban deprivation and ill health, and the approaches needed to tackling them, are discussed below, with special reference to conditions in European cities.