The design of an inexpensive ``boxcar'' integrator for improving the signal‐to‐noise (S/N) ratio of low level repetitive signals is described. The design is simplified by using the timing circuits of an oscilloscope to generate the gate and delay for the boxcar. The S/N ratio can be improved up to 60 dB. It is useful for signals from 500 &mgr;V to 30 mV rms containing frequencies up to 50 kHz, at repetition rates to several kHz. Examples of its use for sine and square waves are included.