By a synthesis of data of many surveys, gravity and magnetic maps were prepared. The density of gravity measurements is about one point per 100 km²; the usual spacing of the lines of the aeromagnetic surveys is 10 km in the southern part of the area investigated, and 20 km north of 76 °N. The potential field maps were analyzed by double Fourier spectrum analysis, transformations, filtering, moving windows analysis and inversions. The results are used to establish a scheme of tectonically relevant lines and structural units of the Laptev Sea and the western East Siberian Sea. Shaded relief maps demonstrate the pattern of the potential fields in the investigated shelf area and a part of the oceanic Eurasia Basin north-west of the Laptev Sea. The Eurasia Basin shows linear magnetic and gravity anomalies parallel to the spreading axis, the Nansen-Gakkel Ridge. In the central Laptev Sea, weak NNW striking anomalies indicate that the main structures strike in the same direction. They show offsets at ENE trending fault zones which may be transfer faults. According to the interpretation of the reflection seismic measurements and gravity modeling the mostly NNW striking M/V A. Lazarev Fault separates the Ust'-Lena Rift Basin from the Laptev Horst. It corresponds to a change in the gravity pattern, but not in the magnetic pattern. Strong magnetic anomalies indicate shallow basic rocks for the De Long Plateau and deep-lying basic rocks beneath Kotelny Island. From southwest over west, northwest and north to northeast, the New Siberian Islands are surrounded by a nearly 50 km wide strip of intense gravity gradients. They may be caused by differential vertical movements. The Khatanga-Lomonosov Zone separates the Laptev Sea from the oceanic Eurasia Basin. Pronounced earthquake epicenters mark the Belkovsky graben and the southwestern Laptev Sea coast. The potential field maps do not indicate oceanic crust for any parts of the Laptev Shelf and the western East Siberian Sea.