An electron current monitor for linear accelerators has been developed. Its sensing element was a toroidal coil through which the beam passes undisturbed. With appropriate electronic circuity this permitted the true shape of the current pulse to be viewed and also provided an indication of the average beam current on a meter. The average beam current that could be measured ranged from 3×10−8to 3×10−6amp. Furthermore, the use of the current monitor greatly simplified the process of initially obtaining yield from the machine.