This paper presents a ray tracing technique to predict path loss and delay spread in buildings. A computer program to predict radio propagation in buildings based on site-specific information such as wall locations and building materials is described. Using geometrical optics-based assumptions, rays are traced in three dimensions from a transmitter location. Line-of-sight, specularly transmitted, specularly reflected, and non-specularly transmitted and reflected rays are included in the model. The individual rays are combined coherently as a function of excess delay to form a power delay profile. Power delay profiles are used for qualitative comparison of measured and predicted propagation. Statistics such as path loss and rms delay spread are computed from the power delay profiles to provide quantitative comparisons. For the office environment studied, reasonable agreement between measured and predicted power delay profiles is found, path loss is predicted to within 6 dB, and rms delay spread is predicted to wimin 20 ns.