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Is your question related to the SEOmoz Webapp? Because, if it is so, the answer is: you can do both. Which is the problem choosing one campaign for all the languages' versions of your site? That you are going to spend more time in order to separate the datas for any version. For instance, if you track 20 keywords per language, you're going to see how your site ranks for an english keyword also in the spanish Google or the german one... Also, when you are going to make link research, you will need to use the Excel filter a lot, in order to see what sites really links to one version or another. If this is not a problem for you (or you have limited campaign spots, being just 5 on a basic Pro level), then, you can create just one campaign... but the ideal (for better job organization) would be to create one campaign for every language version. Ciao