A description of and key to twelve species of Psathyrella section Hydrophilea (Romagn.) ex Sing. emend. Kits van Wav. is given. These species are: P. hydrophila, P. hydrophiloides (spec. nov., = Drosophila pilulaeformis ss. Kühn. & Romagn.), P. laevissima, P. subpapillata (comb. nov.), P. fragrans (an American species found in the Netherlands), P. mucrocystis (= Drosophila chondrodermoides Romagn.), P. frustulenta, P. obtusata with var. utriformis (var. nov.), P. chondroderma, P. pseudocasca (comb. nov.) P. umbrina (spec. nov.), and P. rannochii (spec. nov.). Most of these species are exceedingly rare and some have not yet been recorded from the Netherlands. Type material of P. mucrocystis and Drosophila chondrodermoides has been examined as well as material of P. subpapillata and P. pseudocasca from the Romagnesi herbarium. Of P. frustulenta and P. obtusata only brief descriptions are given as full descriptions have recently been published. The name P. cortinarioides P. D. Orton is considered a synonym of P. frustulenta.