Debris flows can occur almost anywhere in the Swiss Alps. The analysis or past events is an essential tool to obtain basic data in order to assess the risks associated with debris flows. Large-scale storm events resulting in many singel debris flows are helpful for such an analysis. In several Swiss regions, catastrophic storms occurred in 1987 and in 1990; the data obtained formed valuable basis for detailed analysis. Firstly, the meteorological situation (prior conditions, precipitation amounts and intensities) is treated. Secondly, parameters are discussed which characterise the course of debris flow events (event magnitude, maximum discharge, flow velocity etc.).