Localization of iron and other elements in the lichen Nephroma arcticum collected in Sweden (Abisko, N Lapland) was studied under acidic conditions after thalli had been soaked in a 20 mM FeCl2 solution. Twelve elements accumulating in different parts of the thallus were detected via an SEM linked to an energy dispersive X-ray analysis unit. There were no significant differences in Na and Al amounts between the control and the FeCl2-treated samples. The percentages of Fe in apothecial discs, ascospores, necks of apothecia and in thalli of treated samples were higher than in control samples but the percentages in the dorsal part of the dics were similar in the treated and control thalli. The percentage of Cl was higher in all five parts of the lichen samples treated with FeCl2. Lower percentages of K, Ca and Mg were detected in those parts of the treated lichen in which high elevations of Fe and Cl were found. The ratio between "net" percentage of Cl and Fe atoms in discs and in ascospores was found to be closest to the 2.00 value, which occurs in the FeCl2 formula. The accumulation of these two elements, coupled to the leakage of essential ions from lichen discs and ascospores, appears to be deleterious to lichen mycobiont reproductive capacity.