Dear FSL, There seems to be a confusion between the built-in help (result of fast -h; FSL 5.0.9) and the wiki (http://fsl.fmrib.ox.ac.uk/fsl/fslwiki/FAST#fast_COMMAND-LINE_PROGRAM). fast -h says: -b output estimated bias field -B output bias-corrected image While wiki says: -B output estimated bias field -b output restored image (bias-corrected image) Vale, Auer, Tibor M.D. Ph.D. MRC Cognition and Brain Sciences Unit 15 Chaucer Road Cambridge CB2 7EF United Kingdom Phone/Work: +44-(0)1223-273613 Mail: [log in to unmask]<mailto:[log in to unmask]>