The author introduces the use of a ‘synoptical key’ for the species of Asperula, Galium, Rubia and Sherardia occurring in the Netherlands. This key was proposed by LEENHOUTS (1966). The author agrees with Leenhouts that the synoptical key has certain advantages over the more commonly used ‘analytical keys’. For a full discussion of the form and advantages of the different types of keys, see the studies by Leenhouts.