The daily exposureto radiofrequency radiation(RFR) from the wireless communication deviceshas been a subject of debatefor thepast decade, many studies have been carried out to detect possible effectsof the radiofrequency radiationon human and their consequences on human health.The goal of our study was to assess to whetherthe chronic whole-body exposure to non-thermal radiofrequency (RF) radiation from cellular phones could affect the bone marrow cells in mature rats. Twenty-three Wistar rats weighing 116 and 184 g were randomly divided into 4 groupsaccording to time of exposure: control and exposed groups,animals in treatment groups were exposed to 900-MHz RF (217-Hz pulse rate, 2-Wmaximum peak power, SAR 0.873-0.352 w/kg) for: 0h (control), 1h, 2h and 3h daily, 7 days a week for up 15 weeks.. After the period of exposure,bone marrow aspirations were obtained from the femur of all rats.The cell response was assessed by number and type of the bone marrow nuclear cells using our standard laboratory methods. The results revealed that the number of polychromatophilic and acidophilic erythroblast cells in mature rats increased significantly compared with their control group and number of lymphocytes in mature rats decreased significantly compared with its control groupand this effect is less remarkablewith increasing time of exposure.