Background: Pre-exposure to radiofrequency radiations of mobile phones would significantly increase the survival rate of exposed animals compared to those exposed to a lethal dose of gamma radiation alone. Stimulation of the immune system is believed to be a key mechanism for the induction of this phenomenon, the so-called â€œadaptive response.â€ The immune system protects organisms against infection with multiple lines of defense of increasing specificity.Objective: In this animal study, the effect of pre-exposure to radiofrequency on the survival adaptive response of a group of BALB/c mice which received intraperitoneal injections of Escherichia coli was investigated.Methods: Groups of BALB/c mice (exposure groups) were exposed to radiofrequency radiations emitted from a GSM mobile phone for 2, 4, 8 or 12 hours a day for 3 days. Other groups (sham exposed groups) were treated as exposure groups but the mobile phone was switched off during the experiment. On day 4, animals received intraperitoneal injections of E. coli. Survival of the animals was carefully monitored by an expert scientist.Results: 15 days after exposure to the bacteria, the survival rate of the animals exposed to mobile radiations for 12 h/day was significantly (p=0.021) higher than those which only exposed to the bacteria (no pre-exposure to radiofrequency).Conclusion: Pre-exposure of BALB/c mice to radiofrequency radiations emitted from a GSM mobile phone increases their resistance to E. coli infection. This finding may have important clinical implications in treating bacterial infections.