While responding to other topics it occured to me that it might not be a bad idea to poll you on my theory. Myself, my mother and my brother all have CFS or "mystery seemingly related illness". My Grandmother also seemed to have similar issues. My son, on the other hand has Leigh's disease which is a very serious (terminal) mitochondrial disorder. I have read from a couple of sources (one of which is "From Fatigued to Fantastic") that a possible genetic factor in CFS could be related to mitochondrial disease. Mitochondrial DNA is inherited from the mother's side of the family. It passes unchanged (with the exception of spontaneous mutation) from mother to child. I'd like to know: Q1 If you beleive you have inherited suceptibility to CFS, did it come from a maternal line (Only your mother's, mother and so on....your mother's father, for example doesn't count.) or paternal? abd: Q2 Do you know (or are you) a man who seems to have passed suceptibility on to their children?