[en] This report, one of a series of biannual progress reports, describes the status of research and development in the Safeguards and Security Program at Los Alamos from February-July 1981. Most work covered here is sponsored by the Office of Safeguards and Security of the Department of Energy; however, project activities that are technically closely related to nuclear safeguards and security also are included where appropriate for conveying information useful to the nuclear community. The report comprises four major subject areas: Security Development and Support; Nuclear Materials Measurement and Engineering; Nuclear Facility Safeguards Support; and International Safeguards, Technology Transfer, and Training. Some technical topics included in the subject areas are computer and informational security, chemical and nondestructive analysis of nuclear materials, process modeling and analysis, nuclear materials accounting systems, evaluation of prototype measurement instrumentation and procedures in nuclear facilities, design and consultation for facilities, technical exchange, training courses, and international safeguards