On the basis of the geographic distribution of some 200 planktonic dinoflagellates recorded from the Arctic, species ranges were typified. Both original and literary data were considered and occurrences were mapped. The types are as follows: Arctic-boreal, boreal, Arctic-boreal-tropical, tropical-boreal, Antarctic-tropical-boreal, bipolar and cosmopolitan. Each type is discussed separately. Mostly, they correspond to the range types known for planktonic diatoms. The evidences of the unity of the Arctic-Boreal Biogeographic Zone are presented. No purely Arctic species have been found. Low endemism of the dinoflagellates of the Arctic-Boreal Zone at specific level (ca 2%) is noted for the Arctic Ocean. The Arctic-Boreal Biogeographic Zone can be subdivided into the Subarctic-Boreal-Atlantic, Subarctic-Boreal-Pacific and Euarctic Circumpolar subzones. As a whole, the Arctic dinoflagellate flora represents impoverished flora characteristic of temperate waters, mostly of the North Atlantic. The problems of bipolarity and bioindication of oceanic currents as well as the value of the so-called Ortmann and Dunbar lines are also discussed.