This is the first of a series of short papers dealing with Myxomycetes collected by me since August 1951 in the Netherlands, mostly in an area not exceeding 6 square kilometers in extent, situated round Doorwerth in the province of Gelderland, and extending from Heelsum in the West to Oosterbeek in the East, and from Wolfheze in the North to the banks of the Rhine in the South. Localities will only be mentioned by name when the specimens were collected outside this area, or when they appear to be rare here. Species which according to Prof. Dr. W. K. H. Karstens (private communication) have not been found previously in the Netherlands, have been marked with an asterisk. The (unpublished) list of Dr. Karstens, which covers the whole of the Netherlands, contains 18 species that were not found by me.