The thesis describes an investigation of the hypothesis that a number of characteristics of planning and design in Jeddah's recent villa and apartment developments violate established shar=i'ah principles and support socio-cultural consequences which conflict with Islamic tradition. To test this hypothesis, the principles established by the tradition of Islam to govern the social and physical environments of Muslims are analysed. The upholding or violation of these principles is then examined against the planning and design characteristics at the various scales - urban, neighbourhood, and house - of Jeddah's modern housing. The results support the hypothesis. In the course of the study, a set of matrices is constructed to link the degree of violation of principles at the various scales to the degree of obligation associated with each principle. These matrices are based on an analysis of traditional Islamic principles derived from basic shar=i'ah sources, such as the Qur'an and sunnah, and of the factors observed to violate them derived from the general conditions of a recent housing in Jeddah. Their validity as an operational tool for evaluating housing environments is tested for using two case studies of existing housing schemes. The outcome of these tests supports the validity of the matrices and their potential usefulness as an operational tool. Suggestions are made about the development, simplification and further testing of the matrices to enhance their practicality as a general tool for the evaluation of existing and proposed housing. In order to place the research in context, some background is given on shar=i'ah and its sources. The stand of Islam on modernity is explored and the process of the Saudi modernisation that has led to the emergence of Jeddah's new housing form is described.