The changing development of our historic towns and cities is resulting in the need for new uses to be found for historic buildings. As traditional centers lose their economic basis, planners are in a position to direct and change the way the historic district develops. This provides the opportunity for the preservation of historic buildings once an alternative economic framework begins to emerge. The historic buildings are, however, a fragile resource and the genus loci of the district is easily lost to the pressure of commerce. Basic principles involved in the conservation management of historic towns are presented. The use of these principles is considered in the Convent Garden area in London, a now completed and successful piece of urban management, and in the Walled City of Lahore, Pakistan, where work is about to commence. It shows that these principles are applicable with only minor adaptations, irrespective of location and culture.