Multiple rock-magnetic and non-magnetic techniques were employed to identify iron sulfides in late Pleistocene Czech loess deposits. The results indicate that iron sulfides in the loess at Znojmo section are mainly pyrrhotite and pyrite, with stoichiometry ranging from Fe10S11 to FeS2. Although early pedogenic origin of fine sulfide fraction can not be ruled out, scanning electron microscopy (SEM) of individual grains and microscopic observations of magnetic extracts show that iron sulfide grains are probably of detrital origin. Potential sources of these sulfides may have been eluvium loams above hypothetical ore deposits in the vicinity of the section or glacifluvial sediments from nearby glacial margins. Framboidal pyrite forms, now completely replaced by iron oxides, suggest that some particles of biogenic sulfides may have also been transported into loess from presumably fluvial sediments. ¿ 2001 American Geophysical Union