The surface-enhanced resonance Raman scattering (SERRS) activity of a statistically significant number of silver nanoparticles has been studied using a correlated SERRS mapping and transmission electron microscopy (TEM) method. TEM allowed the nature of each entity to be directly identified, and the SERRS activity was obtained from the corresponding SERRS map. Particles in various states of aggregation were analyzed to establish relative activities. It was established that SERRS activity is dependent on the specific batch of colloid tested. By averaging different colloid batches, it was shown that increasing SERRS activity is observed with increasing numbers of particles in the aggregates. By reducing the surface coverage of the particles to the extent that single moieties could be examined optically, the ratio of the relative activities of single particles, dimers, trimers, and larger aggregates was estimated. High-resolution TEM images of a number of active and inactive particles are reported. However, no clear correlation between microstructure and SERRS activity was observed.