A prototype electromagnetic calorimeter module has been constructed using conductive plastic proportional tubes stacked with lead panels. Complete conical towers were formed by finely segmented pick-up electrodes etched on copper clad G-10 panels between which tube arrays were sandwitched. The module was tested by high energy electron and hadron beams up to 175 GeV. Excellent energy and position resolutions were obtained. Rejection of pions against electrons was studied.