Mortality has been observed in Argentinian Austrocedrus chilensis native forests. This research has been directed towards a systematic analysis of symptoms, their evolution during a period of one year, a search for signs and an evaluation of the spreading of mortality. The symptoms described are uniform and characteristic in all affected forests. No visible signs were found. The causal agent is still unknown and the spreading of mortality is in progress causing losses and damage in Austrocedrus chilensis forests in Argentina.