The London Agreement and European Patents.
The Patent Baristas have a good post on the London Agreement and the effect it will have on European patents after implementation on May 1st, 2008. See an excerpt explaining the London Agreement below.
The London Agreement is an international agreement designed to reduce the cost of validating a European patent by reducing the translation requirements at the grant stage, in states which are parties to the Agreement. . . .
In order to validate the European patent in the designated states, it is necessary to file a translation of the entire specification in an official language of the national patent office. . . .
Under the Agreement, if a party state has an official language in common with the EPO, then any translation requirements for validation (Art 65(1) EPC) are removed, meaning that no translation at all will be needed.
Some analysis also provided by the Daily Dose of IP, here.
For more background on the EPO translation requirement to validate a European patent in certain countries, see our previous AT! post, titled EP-Oh! (Information about the European Patent Office).