By applying the technique described by Ascenzi et al. (1973), lamellar samples whose fiber bundles had a transverse spiral course were prepared from osteons with alternating lamellae isolated from human femoral shafts. Especially when their diameter is large with respect to their height, lamellar samples lose the cylindrical shape they normally possess in whole osteons, undergoing spontaneous deformations which suggest a state of initial stress. These deformations are more complex than those contemplated by Volterra's theory of dislocations. Even so, the main features of this theory have allowed us to analyse the state of initial stress. This stress was eliminated by cutting each lamellar sample along a line parallel to its axis. The new shape of the sample was then studied. Two conclusions have been drawn: (a) the capacity of lamellae whose fiber bundles have a transverse spiral course to support a tensile load oriented parallel to the osteon axis depends essentially on a state of initial stress, and (b) calcification plays no basic role in producing this state of initial stress.