[en] More than 1,600 fleas collected in southern Belgium from 48 Common dormouse (Muscardinus avellanarius) and from 126 nests of the rodent have been examined by the author. Monopsyllus sciurorum to be the only regular and abundant flea on this small mammal and in his nest. Other fleas were also found: Ceratophyllus gallinae, Dasypsyllus gallinulae, Megabothis turbidus, M. walkeri, Hystrichopsylla talpae and Ctenophthalmus agyrtes. They must be considered as accidental guests of the rodent. The author shows besides they are great number of bird-fleas in some samples because the dormouse-nests from whose the fleas were taken were built on old tit-nests. Finally, he thinks one cannot conclude that Myoxopsyllus laverani is not a dormouse guest. This species is obviously lacking in the samples but is a very rare flea in Belgium, particularly in Ardennes where the most important part of the examined material was reaped.