Electron linear accelerators (linacs) above 10 MeV are capable of generating significant neutron fluxes, particularly when operating in the X ray mode. This paper describes a prototype passive, integrating system for neutron measurements, based on the plastic etch-pit technique, and the methodology used to determine neutron leakage from linacs. Results are presented from measurements on several machines, and are compared with those obtained using an established gold activation technique. Close agreement was observed. The results also indicate that neutron leakage may be a function of machine age and state of adjustment.