Reduction of usable phosphorus in feed mixtures for hens below the level commonly recommended in the Czech Republic had no a negative effect on the performance and egg quality. Conversely, higher doses of phosphorus with the phytase addition caused deterioration of the performance and the change the ratio of calcium and phosphorus in the diet. Sufficient content of usable phosphorus in the feed mixture is 1.8 g/kg with the phytase addition of 350 FTU/kg. The phytase addition improves utilization of phosphorus. It is also important to monitor the ratio between different minerals in the diet.