Intramedullary fixation is preferred for osteosynthesis in the case of long bone fractures; but the problem of the nails' adjustment to the anatomical needs remains. About 80 cadaveric ulnae were examined to elucidate the curvature of the medullary cavity, the point of varus angulation, the thickness of the radial and ulnar cortical bone and the diameter of the medullary cavity at that point. Furthermore, the point of varus angulation of the posterior border was compared to that of the medullary cavity, to evaluate if it allows any conclusion to the curvature of the medullary cavity. The point of varus angulation of the medullary cavity ranged from 45 to 110 mm (mean 71.02), its angle from 4 to 13.5 grade (mean 8.95). At this point, the thickness of the cortical bone on the radial side was between 2.5 and 7 mm (mean 4.44) and ulnar between 2 and 8 mm (mean 4.37). The diameter ranged from 4 to 10.5 mm (mean 6.96). The point of varus angulation of the posterior border was between 65 and 110 mm (mean 85.88) and differs from that of the medullary cavity observed between 45 and 110 mm (mean 71.02). The point of varus angulation of the posterior border and the medullary cavity differs from 1 to 60 mm and it is found in most cases to be more distal than the point of varus angulation of the medullary cavity so the palpable posterior border allows no reliable conclusion of the curvature of the medullary cavity.