Neuronal cultures, including motoneuron (MN) cultures, are established from embryonic animals. These approaches have provided novel insights into developmental and possibly disease mechanisms mediating cell survival or death. Motoneurons isolated from mouse models of disease, such as the SOD1G93A mouse, demonstrate subtle abnormalities that may contribute to pathology. Nonetheless, in the animal model, pathological events become more prominent as the animal matures, but the ability to isolate individual cells to investigate these events is limited. Here, we describe a protocol derived and modified from previously published protocols to isolate motoneurons from mature animals. While the yield of cells is low, the ability to examine mature motoneurons provides a new platform to investigate pathological changes associated with motoneuron disease.