A cylindrical chamber, 8.5 in. in length and 8.5 in. in diameter, containing two sets of parallel multiple‐wire grids has been built and operated as a proportional counter for fast neutron detection. The collecting wires are 0.001 in. in diameter. Filled with pure CH4at about atmospheric pressure and operated at 3400 v, it serves to detect neutrons up to 10 Mev, with an average efficiency of 0.17 percent. The energy distribution of neutrons from 0.3 to 3 Mev can be estimated. The multiple‐wire counter is completely insensitive to gamma radiation under these operating conditions. This instrument has been used to make a survey of fast neutrons around the U. C. L. A. cyclotron. At higher pressures the instrument can presumably be used to measure neutron spectra of higher energy.