International audiencePurpose: We previously reported the inability of Global System for Mobile communication (GSM) signals at 900 (GSM- 900) and 1800 (GSM-1800) MegaHertz (MHz) to induce morphological and physiological changes in epidermis of Hairless rats. The present work aimed at investigating heat shock proteins (HSP) expression - as a cellular stress marker - in the skin of Hairless rats exposed to GSM-900 and -1800 signals. Materials and methods: We studied the expression of the Heat-shock cognate (Hsc) 70, and the inducible forms of the Heatshock proteins (Hsp) 25 and 70. Rat skin was locally exposed using loop antenna and restrain rockets to test several Specific Absorption Rates (SAR) and exposure durations: (i) single exposure: 2 hours at 0 and 5 W/kg; (ii) repeated exposure: 2 hours per day, 5 days per week, for 12 weeks, at 0, 2.5, and 5 W/kg. HSP expression was detected on skin slices using immunolabeling in the epidermal area. Results: Our data indicated that neither single nor repeated exposures altered HSP expression in rat skin, irrespective of the GSM signal or SAR considered. Conclusions: Under our experimental conditions (local SAR 55 W/kg), there was no evidence that GSM signals alter HSP expression in rat ski