A pollen diagram from Flandrian (post-glacial) organic deposits at Red Moss, Lancashire, has been constructed and six pollen assemblage zones defined. Radiocarbon dating, using equipment described in outline, has been applied to sixteen horizons within this sequence, so that boundaries of the pollen assemblage zones, and significant changes within them, have been dated. The sixteen dates fall between 9798 $\pm $ 200 B.P. and 4370 $\pm $ 80 B.P., and form a consistent series, apart from the basal date, which lies near the Late Weichselian-Flandrian boundary. The sequence of assemblage zones has been assigned to three major chronozones of the Flandrian: FI, corresponding to the first four assemblage zones, covering the period of time before the clear establishment of mixed oak forest; FII, corresponding to the mixed oak forest zone (Quercus-Ulmus-Alnus) starting at 7107 $\pm $ 120 B.P., and FIII, corresponding to the Quercus-Alnus zone, starting at 5010 $\pm $ 80 B.P. The dating of the pollen assemblage zones at Red Moss is briefly compared with dates from other dated long Flandrian sequences in north-west Europe. It is shown that certain pollen-analytically defined horizons associated with the Alnus and Corylus rises have diachroneity while the horizon of the Ulmus decline is broadly synchronous. The significance of these differences is briefly discussed. Many more dated profiles are required before interpretation of these differences can be made in terms of migration, succession or climatic change.