We fabricated nanofluidic channels that have elliptical cross sections with major and minor radii of less than 100 nm, without the use of electron-beam or other high-resolution lithography. The channels were formed by thermal removal of sacrificial polymer nanofibers. The sacrificial template fiber was deposited on a target substrate by electrospinning and encapsulated by a spin-on glass. The elliptical shape of the channels eliminates sharp corners, at which fluid flow is hindered, and provides convenient boundary conditions for theoretical modeling of fluid flow in the channels. Also, the spin-on glass is optically transparent and compatible with chemical analysis, thereby opening up application in biomolecular separation and single molecule analysis. Hundreds of parallel channels have also been formed by the oriented spinning process. (C) 2003 American Institute of Physics.