The 28-28th May fl ood event in the Western Alps: a short report on geomorphological processes surveyed by the IRPI-CNR Institute (NW Italy). A long rainy period in the Western Alps of Piedmont (NW Italy), accompanied by intense snowmelt, ended with heavy rainfall on 28-29th May 2008; maximum daily and hourly rainfall depth attained 300 mm and 50 mm respectively. In a relatively, geologically “weak” valley system with generally weathered bedrock (Calcschist, gneiss and mica schist, quartzite and dolomitic limestone), sometime covered by slope and glacialinherited deposits, with an high relief energy and prone to a weak seismic activity, landforms have been locally remoulded by instability processes due to outcome of ephemeral springs. They often resulted in partially re-activated old landslides and soil slips (by hundreds). Paroxysmal torrential activity, with special regard to massive debris load and sediment delivery, mainly resulted in debris fl ood and debris torrent processes, and partly in debris fl ows. The total amounts of material set in motion in single small catchments accounted for between few hundreds m3 and to several ten thousands m3, involving a casualty (four deaths) in the Pellice Valley.