In this paper, we will investigate microwire fibers for low-loss terahertz transmission. Microwires, air-clad wire waveguides with diameter smaller than the operating wavelength (a few Î¼m), have an enhanced evanescent field and tight wave confinement resulting in a low loss waveguide structure for the terahertz (T-ray) frequency regime. Based on our experimental data for the bulk material absorption of four glasses (F2, SF6, SF57 and Bismuth) and a polymer (PMMA), we calculate the normalized field distribution, power fraction outside the wire and effective loss. It will be shown that regardless of material, the effective loss of all microwires converges to the same order < 0.01 cm-1.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.