We found that people with ME/CFS are more likely to carry certain DNA differences in eight regions of their genome, and these variants tell us about possible biological causes of ME/CFS. Most of these regions contain several genes. Our methods did not allow us to conclusively locate the ones most relevant to ME/CFS in each region, but public data allowed us to pick out the most likely ones. Three of the most likely genes produce proteins that respond to an infection. Another likely gene is related to chronic pain. Overall, our initial genetic results show that ME/CFS is partly caused by genes related to the immune and nervous systems.