The fungi of occidental Catalonia after recent prospections I. This work intends to collect the mycological data gathered during the last four years as a result of the project "Fungal biodiversity of Catalonia", in the western and southern, mainly lowland areas of this country. The climate is mainly dry (400-600 mm/year) and warm. The survey, that covers 160 localities, has enabled the identification of 37 species of Myxomycota, 5 of Zygomycora, 159 of Ascomyctra, 101 mitosporic fungi, 8 Teliomycetes, 1 Ustomycetes, 16 Phragmobasidiomycetes and 92 Apliyllopllorates, that are included in this paper. Because of space limitations, the remaining 326 agarics and 44 Gasteromycetes will be published in the next number of this journal. This work is a contribution to a best understanding of the fungal flora, chorology, ecology and phenology of the West-Mediterranean dry lowlands.