We showed that scanning white light interferometry (SWLI) can provide nanometer depth resolution in 3D topographic analysis of electrospun drug-loaded nanofibrous mats without sample preparation. The method permits rapidly investigating geometric properties (e.g. fiber diameter, orientation and morphology) and surface topography of drug-loaded nanofibers and nanomats. Electrospun nanofibers of a model drug, piroxicam (PRX), and hydroxypropyl methylcellulose (HPMC) were imaged. Scanning electron microscopy (SEM) served as a reference method. SWLI 3D images featuring 29 nm by 29 nm active pixel size were obtained of a 55 mu m x 40 mu m area. The thickness of the drug-loaded non-woven nanomats was uniform, ranging from 2.0 mu m to 3.0 mu m (SWLI), and independent of the ratio between HPMC and PRX. The average diameters (n = 100, SEM) for drug-loaded nanofibers were 387 +/- 125 nm (HPMC and PRX 1: 1), 407 +/- 144 nm (HPMC and PRX 1: 2), and 290 +/- 100 nm (HPMC and PRX 1: 4). We found advantages and limitations in both techniques. SWLI permits rapid non-contacting and non-destructive characterization of layer orientation, layer thickness, porosity, and surface morphology of electrospun drug-loaded nanofibers and nanomats. Such analysis is important because the surface topography affects the performance of nanomats in pharmaceutical and biomedical applications. (C) 2013 Elsevier B.V. All rights reserved.