The present invention relates to a phytase which has at least 74% identity to a phytase derived from Citrobacter braakii and comprises at least one alteration as compared to this phytase. These phytase variants have amended, preferably improved, properties, such as thermostability, temperature profile, pH profile, specific activity, performance in animal feed, reduced protease sensitiliby, and/or an amended glycosylation pattern. The invention also relates to DNA encoding these phytases, methods of their production, as well as the use thereof, e.g. in animal feed and animal feed additives.