A phytosociological synthesis of the segetal vegetation in the Czech Republic was performed using methods of the Zürich-Montpellier school. In total, 712 relevés made by the author in this country in 1955–2000 were classified, and 22 associations and one unranked community were distinguished. Each syntaxon is characterized by diagnostic species, documented by a synoptic table, and the syntaxonomy, structure, species composition, ecology, dynamics, distribution and variability of each syntaxon are commented on. Names are revised according to the rules of the International Code of Phytosociological Nomenclature. All syntaxa belong to the class Stellarietea mediae and associations are assigned to the orders Centaureetalia cyani (alliances Caucalidion lappulae, Fumario-Euphorbion, and Sherardion), Atriplici-Chenopodietalia (alliances Scleranthion annui, Polygono-Chenopodion polyspermi, Arnoseridion minimae, and Panico-Setarion), and Eragrostietalia (alliance Eragrostion).