Hi, How could I efficiently construct a PLINK map file from scratch using a large list of SNP IDs? Unfortunately I don't have the original map file for our data. I've tried the batch search option at the NCBI SNP DB but the output files are not so practical to use. I've also tried to annotate the list from within WGAviewer, which works well for a small list of SNPs, but for several hundred thousands will take for ever. I need four columns, chromosome - rs number - genetic distance ("0" for my purpose) - NT position Any suggestions will be appreciated, Fabio -- Fabio Sánchez, MD, MSc, PhD Unit of Dermatology and Venereology Department of Medicine Karolinska Institute SE-17176 Karolinska University Hospital Phone: +46 8 51772158 Fax: +46 8 51773620 [[alternative HTML version deleted]]