The activities of the Hot Dry Rock Program at Los Alamos are reported in two volumes this year. This volume, in accordance with guidelines provided by the USDOE Geothermal Technology Division, reports our work in an objective/accomplishments format which stresses the relationship of our activities and accomplishments to the program objectives. Because it is designed to serve as a stand-alone document, some sections from previous reports are repeated herein for completeness with little change from previous years. This volume is intended to serve both as a functional report to HDR Program management personnel at the DOE and the Laboratory, and as a useful general reference document to provide a view of the status and accomplishments of the HDR program as of the close of FY91. The companion volume to this report is a compendium of scientific and technical publications of the project staff during Fiscal Year 1991. The compendium is intended to provide the details of the technical information published in this program during Fiscal Year 1991