The excavation, between 1991-1992, ofa branch ofthe Seine in Paris revealed three neolithic dwellings on the south bank: two front the middle neolithic period and one front the end of the neolithic or chalcolithic period. Ten oak dugouts were discovered at the foot of these sites, together with neolitic objects in secondary position, six examples have already been dated using C14 analysis. The weight of the sediment covering these vestiges (which were substantially deformed) and their rather fragmented state, does not allow for a study of their forms. This can only be done at a later stage, after completion of the conservation and restoration process. However, it is essential to proceed with the analysis of the marks left by the tools (or workmanship traces) before this work due to their being barely visible and their superfìcial aspect. The interest ο f these skiffs is not so much in their form (they are all incomplete) as in the building process. Three of them have carbonised traces protruding from the bottom which is, sometimes, exceptionally thin. This proves that the prehistoric people mastered the practice of hollowing out by fire from the beginning of the middle neolithic period (n° 1). The use οf different techniques and tools for making the bottom and sides has also been noted. The first one has a szries of parallel lines with the longitudinal axis, made up of a succession of cupulas produced by hitting with an adze. The sides, however, bear oblique traces (n° 3, 7 and 8) sometimes in the form of a group of offset marks, the layout ο f which indicates the uses ο f axes (also confirmed by the space available for thè handle). Finally, occasionai cubie tenons (n° 4), long tenons (n° 3), cross reinforcement (n° 2) and in the case of the dugout 3, a cross groove have been observed. The latter could well correspond to an original means for controlling the thickness of the bottom during the last stage of hollowing out. Thanks to the analysis of the workmanship traces, sometimes very unclear, the Paris-Bercy dugouts, although incomplete, open new perspectives with regards to their function and building techniques. This analysis would have been impossible, seeing the decomposed and fragmented state of the wood, without an excellent collaboration with the team responsible for the restoration work.