This system uses a large organic scintillator as a moderator for a burst of fast neutrons, many of which are subsequently captured by the hydrogen in the scintillator. The pulses produced by the 2.2-Mev capture γ-rays are observed by four photomultiplier tubes whose anodes are paralleled. The output pulses are amplified and counted by a 10-Mc scaler. The scaler is gated to count for 300 µsec after the pulse, during which interval background is very small. Statistically significant information on total neutron output may be obtained for as few as 103 neutrons per pulse, with practically no upper limit. Relative calibration of the system is simple, and absolute calibrations are stable and reproducible.