Boron‐doped germanium having very low levels of compensation is shown to be useful for detection of far infrared radiation in the 50–125 &mgr; range. The results of measurements of time constant, dc characteristics, photoresponse, and spectral response of several Ge(B) detectors is presented and discussed. Detectors having a peak detectivity of 2.1×1011cm‐cps½‐W−1at 108 &mgr; and a low dynamic impedance have been achieved. The cross section for the capture of a free hole by an ionized boron impurity in germanium at 4.2°K, about 4×10–11cm2, is significantly larger than the corresponding cross section forn‐type impurities in germanium.