Considering these aspects, a key question that this paper will address is whether or not the disk diffusion assay is a suitable method for assessing the antimicrobial nature of nano-metals. The paper will examine the most appropriate approach to differentiate between the particle and the ionic effect thereby helping to interpret the results of the disk diffusion assay for a range of nano-silver particles, coated and uncoated. It will also identify several pitfalls which researchers should be aware of with respect to the processing of nanomaterials prior to testing. The results reported reaffirm the need to characterise the physicochemical properties of the nanoparticle prior to assessing any potential antimicrobial properties analogous to the approach taken in the emerging area of nanotoxicology [28]. Finally the relevance of the results in terms establishing protocols for method development for ‘nanoparticle specific’ antimicrobial properties will be discussed.