A reinforced Butler building was exposed to fallout from Shots Diablo and Shasta, and the resulting dose rates and fallout deposition inside and outside the structure were measured with various instruments and techniques. Protection factors and roof and ground contributions to the total dose rates at points within the structure were determined from the measurements. Comparisons were made with the results of theoretical and other experimental studies. Information obtained from this experiment should be of value as basic experimental data for fallout protection work, although it is recommended that additional substantive data obtained under more controlled conditions.