We have examined Bi-induced surface structures of Si(001), formed in the vicinity of its desorption temperature, by means of scanning tunnelling microscopy and reflection high-energy electron diffraction. Below the desorption temperature, adsorption of bismuth results in a (2xn) Bi-Si(001) reconstruction with second-layer Bi dimers either parallel or perpendicular to the underlying dimers. Even after the desorption of the bismuth epitaxial layer, some bismuth remains on the surface with characteristic structures which depend upon the formation pathway. Perfectly straight Bi lines 1nm wide and hundreds of nanometres long can be formed either by annealing of the saturated Bi epitaxial layer, or by exposure to a large flux of bismuth around the desorption temperature. Exposure to a smaller flux of Bi at the desorption temperature generates a c(4x4) reconstruction. The stability of the c(4x4) reconstruction is thought to be due to a strain effect resulting from incorporated Bi. Both the Bi line and the c(4x4) structures disappear after further annealing and the remaining Bi concentration was below the detection limit of secondary ion mass spectroscopy.