The movements of individually toe-marked wild Mus musculus were detected by tracking the mice on smoked kymograph paper. The smoked paper was placed in unbaited half-gallon milk-carton or coffee-can shelters arranged in a dense rectangular grid. As many as ten records were obtained from an individual mouse in a single night. The method avoids the biases of trap inhibition, learning, and trap fatigue inherent in the mark-and-recapture method, and provides information suitable for the investigation of the theoretical probability density functions of mouse activity.