Four samples of pupal exuviae of Chironomidae (Diptera) were collected from 8 sites of the Ourthe basin from April 1994 to August 1994. These collections were used to determine normal seasonal trends. The samples yielded a total of one hundred and seven species. Seveteen are new to the fauna of Belgium with a possible additional three taxa (*). A taxonomic list of the species with locations, ecological features and periods of sampling is given, in a table which allows comparison with previous checklists.