After twenty years of aerial surveys, a typological analysis of 379 enclosures has been realized on a sampling available at the end of 1989 in northern Brittany. A first distinction appears between enclosures with paracurvilinear ditches (including curved plans) and enclosures with linear ditches, the second ones having often orthogonal sides. For paracurvilinear enclosures (EC), the Whimster's classification has been slightly modified with more convenient types for the area. We can note predominance of single-ditch enclosures, on the one hand, and quadrilateral enclosures, on the other. Regarding sizes, the major enclosed areas vary between 1 000 and 5 000 m2. An analysis of distribution maps for the principal types shows differences. The study of the lengths and widths of rectangular enclosures (RL) shows two principal groups. The regional distribution of these enclosures is more widespread than the EC enclosures. On many sites, we can remark some associations of EC and EL types of enclosures, simply adjacent or superposed. These observations show a continued settlement on the same place, with several development phases. The multiple concentracal ditches can also correspond to different phases. The association of enclosures with gallo-roman material is also analysed.