Thank you Steve. I added the path to my MATLAB directory, however, I am now getting the following error Loading "Sub0501_RD.nii.gz"... Error using fread Invalid file identifier. Use fopen to generate a valid file identifier. Error in read_avw_hdr (line 17) testval = fread(fid,1,'int32'); Error in read_avw (line 26) [dims,scales,bpp,endian,datatype]= read_avw_hdr(tmpname); Error in flica_load (line 41) [vol dims scales bpp endian] = read_avw(Yfiles{k}); I checked my files and they are stored with least significant bit first and I can open them independently with other programs. Thank you for the help with this. dominic