One evolving and increasingly important means of verification of a State’s compliance with its international security obligations involves the application of publicly available commercial satellite imagery. The International Atomic Energy Agency (IAEA) views commercial satellite imagery as “a particularly valuable open source of information.” In 2001, the IAEA established an in-house Satellite Imagery Analysis Unit (SIAU) to provide an independent capability for "the exploitation of satellite imagery which involves imagery analysis, including correlation/fusion with other sources (open source, geospatial, and third party). Commercial satellite imagery not only supports onsite inspection planning and verification of declared activities,” but perhaps its most important role is that it also “increases the possibility of detecting proscribed nuclear activities.” Analysis of imagery derived from low-earth-orbiting observation satellites has a long history dating to the early 1906s in the midst of the Cold War era. That experience provides a sound basis for effectively exploiting the flood of now publicly available commercial satellite imagery data that is now within reach of anyone with Internet access. This paper provides insights on the process of imagery analysis, together with the use of modern geospatial tools like Google Earth, and highlights a few of the potential pitfalls that can lead to erroneous analytical conclusions. A number of illustrative exemplar cases are reviewed to illustrate how academic researchers (including those within the European Union’s Joint Research Centre) and others in Non-Governmental Organizations are now applying commercial satellite imagery in combination with other open source information in innovative and effective ways for various verification purposes. The international constellation of civil imaging satellites is rapidly growing larger, thereby improving the temporal resolution (reducing the time between image acquisitions), but the satellites are also significantly improving in capabilities with regard to both spatial and spectral resolutions. The significant increase, in both the volume and type of raw imagery data that these satellites can provide, and the ease of access to it, will likely lead to a concomitant increase in new non-proliferation relevant knowledge as well. Many of these new developments were previously unanticipated, and they have already had profound effects beyond what anyone would have thought possible just a few years ago. Among those include multi-satellite, multi-sensor synergies deriving from the diversity of sensors and satellites now available, which are exemplified in a few case studies. This paper also updates earlier work on the subject by this author and explains how the many recent significant developments in the commercial satellite imaging domain will play an ever increasingly valuable role for open source nuclear nonproliferation monitoring and verification in the future. ; JRC.E.8-Nuclear security