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I'm not sure how helpful it is, in the sense of being good news, but I did something like this to one of my sites on purpose once, and wrote it up: http://www.seomoz.org/blog/catastrophic-canonicalization A couple of tips: (1) I think what Oleg is saying, which I agree with is that if Page A had a canonical to Page B, instead of just removing the canonical tag, put in a canonical tag pointing from Page A to Page A. Sometimes, the self-referencing canonical will help over-ride the old/bad canonical. (2) Fetch is a good bet, but I'd also re-submit an XML sitemap with just the "bad" URLs. It's not a cure-all, but it can help nudge Google. Unfortunately, it really can take time to sort out. Make sure your internal links are correct as well. You could temporarily build new internal links (list a few resources on your home-page, for example) to push link-juice temporarily. You could also post the proper URLs on Twitter/FB, etc., to kick them a bit. Of course, that only works for a few pages, not for hundreds.