Hello, Thank you all for your sensible advice and references. I'm going to test on my data the different clustering methods / softwares you suggested to me. Just one last thing, it seems that all these methods but the k-modes one are included either in SPSS or R or LCA software, all available from the WEB ; could you indicate me an available program / library (fortran, matlab, etc) that includes the k-modes method so that I can also test it in parallel with the other methods ? Best Regards, Arnaud. ---------------------------------------------- CLASS-L list. Instructions: http://www.classification-society.org/csna/lists.html#class-l