This chapter describes the principles of method used in total neutron counting (as distinct from correlated neutron counting described in Chaps. 17 and 18). In this method only the number of neutrons detected is used to make measurements of uranium and plutonium. The chapter describes the typical chain of electronics from the detector to the recording device. There is a discussion of important practical issues in neutron counting such as neutron detector design and efficiency, and background and room return effects. The chapter gives the neutron emission values from spontaneous fission and (α,n) reactions for plutonium oxide and plutonium fluoride of different isotopic compositions as well as the neutron emission from uranium metal, uranium oxide, uranyl fluoride and uranium hexafluoride for depleted, natural and low enriched uranium. The effect of impurities on neutron production is discussed. The neutron transport in the item is discussed with respect to leakage multiplication and spectrum.