The Biological Weapons Convention (BWC) is widely regarded as a treaty whose provisions are difficult to verify because of the paucity of measures to verify compliance within the treaty framework and the nature of the weapons themselves. Advances in biotechnology and their effect on the perceived military utility of biological weapons have focused international attention on this issue. This article examines the concepts of “adequate” and “effective” verification and argues that the treaty falls under the definition of adequate verification in the United States. For other countries, however, the lack of verification measures is of greater concern. The article describes measures that should be added to the BWC to detect violations and promote compliance with the treaty. These include improved methods of resolving allegations of noncompliance, increased reporting requirements for activities permitted under the treaty, greater openness in biological research, and inspections of laboratories and other facilities.