The development of an efficient gamma radiation detector that reads directly in flux and dose rate has been partially successful. The efficiency of the normal Geiger-Mueller counter is known to fall to a minimum in the region where high efficiency is most often needed, namely in the middle of the Compton scatter region. The interaction probability rises on the low-energy side, due to increasing photoelectric absorption, and on the high-energy side, due to increasing pair production. In the present work, the response to photo-electric and Compton electrons has been increased substantially by using a mesh cathode instead of a solid-walled cathode, together with an appropriate gas filling and an enlarged anode. Characteristics are adjusted bv use of a sliding sleeve.