The sulfur constituents in a Mequinenza lignite (Spain) were characterized using a variety of analytical techniques. The investigation was performed to provide information to scientists and engineers attempting to design methods to remove sulfur from coal and lignite, test new analytical methods directed at characterization of sulfur constituents in fuel, and provide basic analytical information concerning the sulfur constituents in coal and lignite. Such information is particularly useful during the evaluation of coal desulfurization processes. The nature of the lignite and the sulfur components were explored using standard ASTM methods; petrographic techniques; mineral analysis using microscopy and X-ray diffraction; low-voltage, high-resolution mass spectrometry (LVHRMS); sulfur L-edge X-ray absorption near-edge structure spectroscopy (XANES); sulfur K-edge XANES; electron paramagnetic resonance (EPR); and controlled atmosphere programmed temperature oxidation (CAPTO). The Mequinenza material is a lignite containing 13.6 % sulfur (maf) and 21.6 % (dry) ash. The sulfur is primarily organic sulfur (12,80 %) and contains smaller amounts of pyrite and very little sulfate. Microscopic analysis showed that clay minerals were the most abundant minerals and that the lignite consisted mainly of the macerals huminite and liptinite. A small amount of elemental sulfur was also detected (L mu g/g) in a tetrachloroethylene extract. LVHRMS analysis of a pyridine extract showed that molecular formulas consistent with thiophenes, aryl sulfides, their corresponding oxidized forms, and disulfides were present. Results from sulfur L-edge and K-edge XANES spectroscopy on the whole lignite were in quantitative and qualitative agreement with LVHRMS results on the pyridine extract with respect to thiophenes. Sulfur L-edge XANES indicated that 40 % of the sulfur was present as thiophenes and 20 % as aryl sulfides. CAPTO reports the sum of these two sulfur forms as 60.4 wt %. The CAPTO and sulfur L-edge XANES results are in excellent agreement. The L-edge XANES indicated that 20 % of the sulfur was present as aliphatic sulfides and 20 % as disulfides. Results of the K-edge XANES analysis indicated that nonpyritic sulfur was distributed as follows : 10 % disulfide, 33 % sulfide, 42 % thiophenic, 9 % sulfoxide, and 5 % sulfate. CAPTO results indicated that 34.4 wt % of the sulfur was present as nonaromatic sulfur. The W-band EPR spectrum was unusually rich in features compared to other coals. These signals are attributed to aromatic radicals that are either purely hydrocarbon or heteroatomic in nature.