An electronic cell detector which provides good cell volume distribution is described. Consideration has been given to bandwidth and input noise with respect to aperture size and resistance. The instrument uses a low noise current pre-amplifier, and switched upper and lower bandwidth providing an overall response time of 5 μsec. It produces a shaped output pulse suitable for most pulse height analyzers and also records the total cell count and time taken for a given volume measurement, which provides an instant check if the aperture becomes partially blocked.