The Los Alamos National Laboratory is conducting rock fragmentation research in oil shale to develop the blasting technologies and designs required to create a rubble bed for a modified in situ retort. This report outlines our first field experiments at the Anvil Points Mine in Colorado. These experiments are part of a research program, sponsored by the Laboratory through the Department of Energy and by a Consortium of oil companies. Also included are some typical numerical calculations made in support of proposed field experiments. Two papers detail our progress in computer modeling and theory. The first presents a method for eliminating hourglassing in two-dimensional finite-difference calculations of rock fracture without altering the physical results. The second discusses the significant effect of buoyancy on tracer gas flow through the retort. A paper on retort stability details a computer application of the Schmidt graphical method for calculating fine-scale temperature gradients in a retort wall. The final paper, which describes our approach to field experiments, presents the instrumentation and diagnostic techniques used in rock fragmentation experiments at Anvil Points Mine.