An ultrahigh vacuum LEED system has been modified for carrying out step kinetic nucleation studies. A substrate heating oven giving accurate, reproducible (±5 °C) surface temperatures, a condensate evaporation oven, a water-cooled quartz crystal microbalance, and a silicon monoxide evaporation source are described. Operating conditions and procedures leading to the attainment of number densities of nuclei reproducible to within a factor of two and nucleation rates accurate to within ±30% are discussed.