This paper presents results for the Specific Absorption Rate (SAR) when using a mobile phone equipped with a multiple antenna system. The SAR is evaluated using the Finite Difference Time Domain (FDTD) method for different configurations taking into account all possible simultaneous transmission from a mobile phone. The considered signals are GSM900, GSM1800, UMTS2100 and WiFi2400. The results show that the calculated local SAR for the different configurations never exceeds the limit of 2 W/Kg recommended by ICNIRP. It was demonstrated also that the maximum of the sum of the SAR evaluated from two different transmitters is always less than the sum of the maximum evaluated ones from each transmitter separately.