The BnF and OCLC have recently announced that they will be loading about 13.2 million catalog records from the BnF into OCLC's WorldCat database. This will make it much easier to discover whether the BnF owns a title that you are looking for, and will be especially useful for identifying rare and unique items in its collections.
This news represents the sustained effort that OCLC is making to internationalize its database. Catalog records for non-English-language materials now make up more than 50% of WorldCat's records.
For more information, please see the press release.