We collected 18,051 DNA samples from people with ME/CFS across the UK. After DNA extraction, genotyping and quality control, we had data for 16,730 samples suitable for GWAS analysis. We then matched the ancestry of the participants samples with those of the control group to ensure consistency, this meant 15,579 DNA samples were used for these initial results. We then compared these samples to a population of 259,909 people without ME/CFS. These large numbers allowed us to find genetic differences across the two populations. Future research could build on our results, through analysis of all DNA data collected.  Researcher access – DecodeME