In this study, the radially thinning liquid sheets formed by a simple splash plate nozzle were investigated. These sheets, observed using high-speed video and 16 mm photography, were found to breakup by way of a localized rupture mechanism. The sheet is thinned by geometric distortion due to the radial expansion of the sheet, and by stretching caused by the presence of large amplitude sinuous waves. The downstream sheet thickness in the wave-thinned region was calculated from experimentally measured perforation growth rates. These thicknesses were found to be about 12 percent of the predicted value for an undisturbed sheet. Trends in the downstream position at which significant thinning due to sinuous waves is predicted to occur agree with trends in experimentally measured rates of hole formation.