The application of total internal reflection microscopy (TIRM) to the inspection of subwavelength optical features on surfaces has been well documented.^1–3 This paper discusses recent experiments testing the feasibility of using TIRM to study dielectric coatings in the nucleation stage. Samples were coated with thin films of different thicknesses to allow optical scattering levels to be determined as a function of coating thickness. An increase was observed in scatter levels with increasing coating thickness, and is assumed to be related to thin film microstructure. Thus, TIRM provides a means of detecting film defects in the early stages of coating growth, as well as identifying possible precursors to nodules that are often observed in thin and thick films.