OBJECTIVE: To investigate the effects of exposure to a 900 megahertz (MHz) electromagnetic field (EMF) on the adolescent rat liver. STUDY DESIGN: Twenty-four male Sprague Dawley rats, aged 21 days, were assigned to 3 groups: control, sham (SGr), and EMF exposure (EGr). EGr rats were exposed to a 900 MHz EMF for 1 h/day in a special cage throughout the adolescent period, while SGr rats were exposed to pseudo-EMF exposure in the same cage. All rat livers were removed on postnatal day 60 and subjected to histopathological and biochemical procedures. RESULTS: Evaluation of histopathological EGr slides stained with H & E revealed loss of hepatocytes, dilated sinusoids, and paleness around pericentral regions. EGr slides stained with Masson's trichrome revealed paleness in hepatocytes around the central vein. EGr TUNELstained sections contained notably more apoptotic cells than did those of the other groups. EGr mitotic and apoptotic indices were statistically significantly higher than those in the other groups. Biochemical analyses revealed that malondialdehyde and glutathione levels increased and catalase levels decreased in the EGr as compared to the other groups. CONCLUSION: The study findings show that exposure to EMF throughout adolescence can lead to oxidative damage and increased apoptotic injury and mitosis in hepatocytes in the male rat liver. © Science Printers and Publishers, Inc.