The aim of this work was to study the oxidative profile of digestive glands of two limpets species (Nacella (Patinigera) magellanica and Nacella (Patinigera) deaurata) exposed to different environmental conditions. The intertidal population of N. (P.) magellanica is subjected to a wide variety of stresses not experienced by N. (P.) deaurata. Although a typical electron paramagnetic resonance (EPR) spectrum of ascorbyl radical in digestive gland from both limpets was observed, neither ascorbyl radical content nor the ascorbyl radical content/ascorbate content ratio was significantly different, suggesting that the difference in the environmental conditions did not appear to be responsible for developing alterations in the oxidative status of both organisms at the hydrophilic level (e.g. cytosol). Lipid peroxidation in the digestive glands was estimated, both as the content of thiobarbituric acid reactive substances (TBARS) and as the content of lipid radicals assessed by EPR, in both organisms. TBARS and lipid radical content were 34.8 and 36.5%, respectively, lower in N. (P.) magellanica as compared to N. (P.) deaurata. On the other hand, total iron content and the rate of generation of superoxide anion were 47.9 and 51.4%, respectively, lower in N. (P.) magellanica as compared to N. (P.) deaurata. The activity of catalase and superoxide dismutase (SOD) was 35.3 and 128.6% higher in N. (P.) magellanica as compared to N. (P.) deaurata, respectively. No significant differences were determined between the digestive glands of both molluscs regarding the content of total thiols. alpha-Tocopherol and beta-carotene content were significantly lower in N. (P.) magellanica as compared to N. (P.) deaurata. A distinctive EPR signal for the adduct Fe--MGD--NO (g = 2.03 and a(N) = 12.5 G) was detected in the homogenates of digestive glands of both limpets. A significant difference in the content of the Fe-MGD-NO adduct in digestive glands from N. (P.) magellanica and N. (P.) deaurata (491 +/- 137 and 839 +/- 63 pmol/g FW, respectively) was observed. Taken as a whole, the data presented here indicated that coping with environmental stressing conditions requires a complex adjustment of the physiological metabolic pathways to ensure survival by minimizing intracellular damage. It is likely that N. (P.) magellanica has a particular evolutionary adaptation to extreme environmental conditions by keeping iron content low and antioxidant activities high.