Abstract Flexible electronics are envisioned to play a major role in future wearable medical devices. An important component of this technology is flexible antennas. This paper presents a preliminary study of on-body and off-body propagation channels in Body Area Networks (BAN) using a small Ultra WideBand (UWB) flexible wearable antenna. The research is carried out with physical measurements in an anechoic chamber and a small laboratory room. The on-body measurements include propagation channels between two wearable devices placed on the head and various locations on the arm (i.e., shoulder to wrist). The off-body measurements cover propagation channels between a head-mounted device and an external device placed at various distances from the body. The wearable devices in these measurements use a small flexible antenna that can easily conform to the surface of the body. The measurements are conducted to better understand and characterize the wireless communication channels in applications such as brain monitoring or brain computer interface. The measurement results show that the UWB flexible antenna presented here performs well for both on-body and off-body communication channels.