There's no easy way of doing this without heavily modifying SPM. The reason why SPM5 produces .img and .hdr files instead of .nii files is that we have a backup system at the FIL. Files that are modified are backed up more frequently, and I figured it would not be such a good idea to have the entire .nii file backed up whenever a little modification is made to a header. Best regards, -John -----Original Message----- From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]] On Behalf Of Mateus Joffily Sent: Monday, December 04, 2006 8:34 PM To: [log in to unmask] Subject: [SPM] .nii files Hi, Is there a way of forcing spm5 to write the image files with '.nii' extension, instead of '.hdr+.img'? Thanks for your help, Mateus