Meltblowing is a unique one-step process for producing self-bonded fibrous nonwoven membranes directly from polymer resins, with average fiber diameter ranging between 1 and 2 mu m. Determining routes for making nano- or submicron-fibers using this process are desirable since there are many manufacturing assets that are already in place. It is envisaged that these nonwoven membranes will find applications in critical areas such as medical, hygiene, filtration, bioseparation, and others. In this study, we investigate the influence of different die configurations and operating conditions on fiber and web characteristics. We also report on strategies for reducing the fiber size below one micron to achieve higher filtration quality at lower basis weight relative to the conventional meltblown webs. Their performance is compared to a control meltblown sample produced by using a typical die design. We find that production of nano-meltblown membranes with an average fiber size in the range of 300-500 nm using this new die design is possible and report on process operating conditions that result in such structures. These samples achieve equal filtration efficiencies to that of our control sample at 88% reduced basis weight but at a lower polymer throughput. The lower basis weight also resulted in a lower pressure drop and overall, the new samples exhibited a higher quality factor, twice that of the control. These results show significant promise for the use of nano-meltblown fibers in filtration applications. (C) 2012 Elsevier B.V. All rights reserved.