Due to the process of subduction of the Nazca Plate, high seismic activity is observed near the Argentine Andean range between 21~ and 36~ The new version of the Argentine Seismic Catalogue, which includes well-defined events during the period 1964-I989, allows us to perform an analysis of seismic risk. Earthquakes with epicenters in the provinces included in the north-western and western regions were studied using Gumbel III extreme value distribution. Modal extreme magnitudes and return periods were calculated for both regions and the results were compard with the ones obtained through the entire process techniques (both analytical and graphical). As a first study, we analyzed each province separately, after which mean values for each region were obtained. Modal values around 5-5.5 have been found and times of recurrence for events with m b > 6 of approximately 25 years were obtained.Facultad de Ciencias Astronómicas y Geofísicas