Discovery of five species of Acarosporaceae that are new to Switzerland or rare. Observations of five rare lichens belonging to the Acarosporaceae family are presented. Three species are published for the first time for Switzerland (Acarospora adscendens, Myriospora dilatata and M. scabrida). The two others (Acarospora albomarginata and Timdalia intricata) are second observations. All five species have been collected in the canton of Valais, and one (A. albomarginata) has also been found in the canton of Grisons. The records of A. adscendens and M. dilatata are the first in the Alps.