One of the most striking recent discoveries in cell biology is that organelles such as mitochondria move between cells. While mitochondrial transfer has now been shown in a variety of settings, both in culture and in vivo, it is not apparent what the consequence of transfer is, or what regulates transfer. We will look at the role of mitochondrial injury in two related systems, neurodegeneration and neurological cancer. These two diseases involve the same cell types, but with a different cellular outcome – either death of the cells in neurodegenerative disease, or survival and proliferation of the cells in cancer. Mitochondria will be fluorescently labeled, injured by chemotherapy and metabolic stressors, then followed by live microscopy to see the consequences on mitochondrial movement between different cell types. This fundamental process has implications for treatment strategies in both neuro-oncology and neurodegeneration.