We report a single-crystal growth technique for strontium ruthenates. Strontium ruthenates exhibit intriguing magnetic properties such as spin-triplet superconductivity in Sr2RuO4. To obtain pure single crystals of strontium ruthenates (Sr2RuO4, Sr3Ru2O7 and SrRuO3) we employed a conventional floating-zone method. For the crystal growth of Sr2RuO4, no severe difficulties are known. Even in air, it is possible to grow that single crystal from the molten zone of polycrystalline bar of SrRuO4. However, for Sr3Ru2O7 and SrRuO3, it is impossible to obtain single crystals by the same procedure. We herein show the importance of oxygen-partial pressure in the atmosphere for the crystal growth of strontium ruthenates based on our successful results. (C) 2002 Elsevier Science B.V. All rights reserved.