Analysis of mouse behavior often requires expensive equipment and transfer of the mice to new test en- vironments, which could trigger confounding behavior alterations. Here, we describe a system for track- ing mouse behavior in home cages using a low-cost USB webcam and free software (Fiji and wrMTrck). We demonstrate the effectiveness of this method by tracking differences in distance traveled, speed, and movement tracks between wild-type mice and amyotrophic lateral sclerosis (ALS) model mice (SOD1G93A).