Continous filament nonwovens are fabrics produced by the direct lay processes, wherein webs are made directly from fibers as they are being spun from molten plastics. These processes eliminate intermediate steps in the production of fabrics, and they provide opportunities for increasing production and cost reduction, although the flexibility in product ranges might be limited. The two important processes in this category are spunbonding and meltblowing. In spunbonding, the fabrics are produced by depositing extruded spun filaments onto a collecting belt followed by bonding of the fibers. There are several process variables that have an impact on the structure and properties of the fibers, and consequently on the structure and properties of the bonded fabric. Although there has been a significant technological advance, the scientific understanding of the process has been limited. Effects of some of these variables have been investigated over the past few years. There has also been some effort to simulate the process by mathematical modeling. A summary of the advances in understanding the evolution of structure and properties during filament formation and thermal bonding is discussed in this paper. (C) 2002 John Wiley & Sons, Inc.