Thanks Graeme, Here's a link to the txt files and the converted ti3 files http://www.symphonyphoto.com/argyllcms/measurementFiles.zip The command arguments I'm using with average are: average CM_Silver_Rag_918_1.ti3 CM_Silver_Rag_918_2.ti3 average.ti3 And then after that... colprof average Colprof returns the error: "colprof: Error - Input file doesn't contain field SPEC_000" I looked at it in a text editor and indeed it (the ti3 files) does not which would suggest I did something wrong with the txt2ti3 tool BUT.... If I'm not mistaken the "SampleID" keyword in the Measure Tool generated txt file should correspond to "SAMPLE_ID" in the ti3 file (the X-Rite file tagging each field with nm and argyll tagging it with SPEC_). Should there be an nm000 entry in the txt file? If so it doesn't appear to be there in any of the measurement files I have (I checked measurement data generated both from the Measure Tool and from Eye One Match). Cheers, Joe