Mobile phone industry has significantly gained the market in last few decades. People are in so much habit of keeping mobile phone with them in their daily life. As the number of mobile phone users is increasing rapidly, it has become main concern to focus on the effect of radio frequency of electromagnetic radiations produced by mobile phone. The EM radiation is called the fourth pollution source besides air, water and noise by the environmentalists. And how to protect against it and calculate it grows to a primary problem. In this thesis, the maximum specific absorption rate (SAR) averaged over 1g and 10g of tissue inside homogenous human head model has been investigated for dual-band PIFA antenna operating in the 900 MHz and 1800 MHz frequency bands. The human head model consists of a uniform core representing human brain, surrounded by shell representing head skull and skin. All simulations are performed using CST-Microwave studio. The provided antenna is tuned in the presence of head because the provided antenna has a very bad performance. then, the antenna is re-tuned again for the presence of head and hand. Simulation of the effect of the hand on antenna performance shows that the performance of antenna is affected significantly because of hand presence. SAR is obtained at various distances between the head and mobile and at various output powers with and without the proposed shield. It is shown that SAR decreases as the distance between the head and the mobile phone increases. The calculated maximum average SAR values in the head is compared with SAR limits in the safety standards of the International organizations. The maximum local SAR becomes more than the FCC and ICNIRP’s upper safety limits for high output powers. SAR reduction issue is considered in this thesis also. Reducing SAR in the head model is effectively achieved by attaching a shield on a mobile phone. The designed shield is made from ferrite and aluminum material. The results reveal that the use of the proposed shield will reduce effectively the SAR value averaged over 1g and 10g of tissues by 53.68% and 58.22% respectively for 900 MHZ band and will reduce the SAR averaged over 1g and 10g of tissues by 63.72% and 61.03% respectively for 1800 MHZ band. Also SRF increased as the Ferrite thickness increased. Finally, the mobile user maximum safe usage time is considered in this thesis, and the results show that the maximum safe usage time should not be exceed one-half hour.