A technique for fabrication of platinum (111) single crystal ultramicroelectrodes (scumes) of disk shape with diameters from 25 to 50 mum is outlined. The fabricated scurries encapsulated in soft sodium glass can be annealed in a furnace at temperatures up to 700 degreesC. The current voltage curve of the Pt scume in 0.5 M sulfuric acid shows adsorption/desorption states of hydrogen typical for platinum (111) surfaces in the given region of potentials. This indicates that the surface of the fabricated single crystal ultramicroelectrode is clean and well oriented. The method chosen for growing the platinum single crystals utilizes long annealing of platinum microspheres in a methane flame for several hours. Crystals produced this way developed all eight (111) and six (100) facets. Development of large (100) facets has been observed on all beads annealed for more than 30 min. Depending on the time of annealing this method can also produce crystals with the shape of a truncated octahedron. (C) 2003 Elsevier B.V. All rights reserved.