Samples of alpha-Fe (Armco) have been deformed by 50% and subsequently annealed at 400 degrees C which is considerably below the conventional recrystallization temperature. The geometry of the grain boundaries has been studied through measurements of the grain boundary traces revealed on longitudinal cross-sections of the specimens. Two etching conditions were employed, one of which revealed networks containing only grain boundaries (designated GB in the further text) whilst the other resulted in delineating the 2-dimensional regions characterized by the presence of sulfur (designated S-GB). Changes in the geometry of these two types of grain boundaries as a result of plastic deformation and annealing are discussed in terms of in-situ high angle grain boundary formation and annihilation.