Hi Is all the results are in the same space (e.g. MNI space for multi-subject output) then you can average the output using fsladd: fsladd AVERAGE.nii.gz -m <list_of_files_to_be_averaged> Cheers, Saad On 6 Jun 2016, at 03:26, Versha Kgan <[log in to unmask]<mailto:[log in to unmask]>> wrote: I want to use FSL to create an average tractography out of many tractographies generated by many DTI samples. I was wondering where I can find this information and which functions in FSL I should be using. I greatly appreciate any advice as I'm new to FSL.