This dissertation describes a geometrical optics model to predict propagation in buildings for personal communication system (PCS) design. Background on the growth of wireless communications is given, and the importance of accurate propagation models is discussed. The peculiarities of propagation in mobile and portable radio environments, particularly multipath propagation and its effects on transmitted signals, are described. Current in-building propagation models are presented and the progression from statistical in the presence of scattering bodies are merged with a site-specific description of the propagation environment to improve upon the accuracy of existing propagation models. A geometrical optics ray tracing model for predicting propagation based on a building blueprint representation is developed for a transmitter and receiver located on the same floor inside a building. The measured and predicted propagation data are presented as power delay profiles that contain the amplitude and arrival time of individual multipath components. Measured and predicted power delay profiles are compared on a location-by-location basis to provide both a qualitative and a quantitative measure of the model accuracy. The concept of effective building material properties is developed.and the effective building material properties are derived for two dissimilar buildings based upon comparing measured and predicted power delay profiles. Time delay comparison shows that the amplitudes of many significant multipath components are accurately predicted by this model. Path loss between a transmitter and receiver is predicted-with a standard deviation of less than 5 dB. Ideas for improving the accuracy and expanding the applicability of the models applied here to wireless in-building propagation prediction are suggested. / Ph. D.