Hi am using the same exact mtz data file from CCP4 uniquefy for two refinements in phenix. I did one round of refinement in phenix 1.3 and then used the output pdb of that refinement and input into the next round of refinement . Only I switched versions to phenix version 1.4. Most other things weere the same including the resolution cutoff used and the input mtz. But phenix tells me that the md5checksums dont match. i am very sure its the same input mtz and identical data resolution ( both cases specifying refinement.input.xray_data.high_resolution=3.0) Could this message of mismatched checksums be an error due to chaging versions midtsream . I certainly dont want to be trampling on my Rfree reflections but apart from copying files to a new directory for the next round and changing phenix versions I have changed little else Thanks for your help in advance hari