Monitoring covert offensive biological weapons research from afar has always been a daunting task. The problems facing analysts today are even more difficult, as advances in life sciences and dual-use biotechnology are rapidly spreading the knowledge, equipment, and materials needed to produce crude and sophisticated biological weapons around the world. Unlike nuclear programs, a well-defined and limited set of equipment and material that can be controlled through various import/export controls does not exist. Future monitoring will become more challenging as the distinctions among military, civilian and dual-use research and applications continue to blur. Managing proliferation risks in this environment will constitute the greatest challenge to policymakers in the biological weapons arena over the next two decades.