This paper describes ultra wideband (UWB) radio propagation measurements and modeling for wireless body area network (WBAN) applications in different environments. Several propagation measurement campaigns and associated modelings were carried out in either a radio anechoic chamber or a specific room type; however, dependence of the radio propagation on surrounding environments was not studied. Multipaths (mainly reflected from floor, ceiling, and walls) highly depend on the environment. To address this problem, radio propagation around the human body was measured in a radio anechoic chamber and four different-sized rooms. Parameters in a conventional loss model derived from the measurements were found to significantly diverge and depend on room volume and line-of-sight (LOS)/non-LOS (NLOS) cases. A modified model considering the impact of room volume has been proposed for the LOS/NLOS cases. Different propagation mechanisms were discussed along with parameter derivation. Probability distributions for the UWB propagation losses were also examined.