TEM-wave scattering from a coaxial aline with a material-filled cavity is studied to obtain the reflection and transmission coefficients in a rapidly convergent series. Their behaviors are studied in terms of medium permittivity, coaxial geometric structure,and frequency. The measurement is performed with a water-filled cavity at 1-3 GHz, and is compared with the theory. (C) 2000 John Wiley & Sons, Inc.