In this study, we have investigated the toxic effects of tobacco smoke obtained from cigarettes treated in pulsed electromagnetic field in the rat. The treatment of cigarettes was accomplished before the initiation of animal studies after exposure of standard cigarettes to pulsed electromagnetic irradiation of low power (>10 -7 W) and wide frequency spectrum (30 Hz to 300 GHz) during 24 h according to the technology described in patents WO 01/26493, EP 1092354, US 2004/0206366A1 and AU2933700 entitled "Method for the Qualitative Improvement of the Products of Tobacco Plant". Rats of both sexes were exposed to tobacco smoke obtained after burning 16 or 32 cigarettes per day during 90 days. The toxicity was assessed on the basis of clinical appearance, changes in behavior, biomarkers of exposure to tobacco smoke (carboxyhemoglobin in blood and thiocyanates in serum) and histopathological and morphological analysis of the lungs of all animals included in the study. The results obtained have shown that, the smoke generated from treated cigarettes formed significantly lower amount of carboxyhemoglobin in rats of both sexes when compared to standard nontreated cigarettes and the effect was dose-dependent. Tobacco smoke obtained from standard nontreated cigarettes induced significant dose-dependent increase of thiocyanate concentration in serum. However, in rats exposed to the smoke of treated cigarettes, there were no differences in thiocynate concentration when compared to controls not exposed to tobacco smoke. The results of morphometrical analysis in the rats exposed to tobacco smoke generated from standard nontreated cigarettes have shown statistically significant and dose-dependent decrease in participation of the lung parenchima in total lung surface up to 34% in male rats and up to 18% in female rats exposed to the higher dose of nontreated cigarette smoke. In addition, in these rats the mean alveolar circumference was incresed for about 17%. In rats exposed to the smoke of treated cigarettes there were no histopathological changes and differences in morphometrical parameters when compared to control animals. In conclusion, the results of this study have shown that, after treatment of cigarettes in pulsed electromagnetic field, the cigarettes produced tobaco smoke that was much less toxic in rats of both sexes exposed by inhalation route during 90 days when compared to the same cigarettes that were not treated in electromagnetic field.