The cytogeography of Taraxacum sect. Taraxacum, Hamata and Erythrosperma has been established for Belgium and northern France. On the basis of collections of samples from field populations and from herbaria the following patterns emerged: in the most nort-westem parts of France and the central zone of Belgium (Toumai/Gent-Liege) diploid, sexual specimens are of fairly common occurrence; diploids are rare or absent in the coastal and northern parts of Belgium as well in the southern Ardennes and in a region from Le Mans-Orleans-Strasbourg to the north: there is an as yet not fully explained disjunction in the distribution pattern of the diploids. In the studied areas no diploids are found belonging to the sections Hamata and Erythrosperma. From the herbarium specimens and from the literature it became clear that in the Belgian Taraxacum flora, which phytogeographically belongs to the north-west European one, many species of the sect. Taraxacum are both present as diploids and triploids: about 30% of the species studied (± 75). In the discussion attention has been paid to the evolutionary dynamics of this section and to the obviously growing need to reconsider the (micro-)systematics of the group.