In this chapter, a first assessment of nanotechnology (NT) within the framework of preventive arms control is done. These criteria are applied to the potential military NT applications in Section 6.1, and to those that are conceivable with molecular NT – in general terms – in Section 6.2. The summary evaluation in Section 6.3 arrives at seven potential NT applications where preventive limits are highly important. Options for the design of such limits are discussed in Section 6.4, considering also positive uses and verification aspects. The final Section 6.5 presents a few meta-aspects of preventive arms control that have come up in the present work.