The present invention relates to phytase variants derived from a parent phytase which is homologous to a Peniophora lycii phytase and comprises at least one substitution in at least one of a number of positions corresponding to a position in the Peniophora lycii phytase. The variants are of improved properties, in particular of a higher specific activity and/or more thermostable than the parent phytase, e.g. of a Tm of up to 82.degree. C. at pH 5.5, as determined by DSC, and/or of a doubled specific activity. The invention also relates to DNA encoding the phytase variants, methods of their production, as well as the use thereof, e.g. in animal feed and animal feed additives.