The dislocation behavior in unirradiated as well as neutron irradiated stainless steel was investigated by the thin-film technique in the electron microscope. Irradiation of stainless steel does not cause defects which give rise to discernible diffraction effects. Instead radiation damage seems to consist simply of a strong supersaturation of point defects, possibly in the form of some type of three-dimensional aggregate, without associated stress field. The supersaturated point defects, which also are present to some extent in the non-irradiated material, cause “old” dislocations to be firmly anchored, lead to some climb during glide in “new” dislocations in thin foils and, by inference, cause the mechanism of “mushrooming” in bulk material. Some additional observations on network formation and on dislocation trails are related, and tentative explanations given.