We have done a mycosociological and taxonomical comparative study of the Agaricales s. l. that fructify in Nothofagus forests and Pinus radiata plantations from the Cordillera de la Costa, the Depresion Intermedia and the Cordillera de los Andes, X Region, Chile. In the forests of Nothofagus the percentage of mycorrhizal species changed from 30.6 % to 52.2 % and the saprophytic one changed from 47.8 % to 69.4 %. In all the native forests studied, we found the following mycorrhizal species: Amanita diemii, Cortinarius magellanicus, Russula fuegiana and Tricholoma fusipes, all of them associated to different species of Nothofagus. The species of the genus Boletus and Stephanopus associated to Nothofagus dombeyi, N. obliqua and N. alpina were only found in the native forests of the Cordillera de la Costa, while Amanita aurantiovelata and Russula nothofaginea associated to N. dombeyi and N. obliqua were only found in the forests situated in the Depresion Intermedia. In Nothofagus forests of the Cordillera de los Andes we have not found any characteristic mycorrhizal Agaricales. No species of Lactarius genus were recorded in native forests, but in those with some kind of anthropic disturbance or situated near Pinus radiata plantations, we found the mycorrhizal species Amanita rubescens and Xerocomus rubellus associated to N. obliqua. The species of the genus Mycena dominated among the saprophytic Agaricales in all the Northofagus forests, We also detected the presence of the genus Armillariella, Gymnopilus, Hypholoma, Pholiota, Pluteus and Psathyrella that fructify on stems and stumps. We did not find any species of pathogenic Agaricales which indicates that the forests are healthy. In the Pinus radiata plantations, the percentage of mycorrhizal species varied from 62.5% to 77.8% and it comprises species of the genus Amanita, Hebeloma, Laccaria, Lactarius, Russula, Suillus and Xerocomus, none of them being dominant. The percentage of saprophytic species varied from 22.2 % to 37.5 %. The low percentage of saprophytic versus mycorrhizal species indicates the poor degradation of the plant remains rendering an accumulation of them, an absence of returning of basic elements and immobilization of nutrients, since the saprophytic native species belonging to Agaricales apparently can not do that function.