A pixel circuit includes an OLED, an OLED driving block, a first switch, and a second switch. The OLED has an anode and a cathode connected to ELVSS. The OLED driving block connected between the anode and ELVDD controls a driving current flowing through the OLED, a first switch is turned on or off responding to a first control-signal and transfers a sensing-bias-voltage to the anode when turned on. The second switch is turned on or off responding to a second control-signal and transfers a deterioration-sensing-voltage to the anode when turned on. In a display mode, the first and second switches are turned off. In a deterioration sensing mode, the first switch is turned on and the second switch is turned off during a first time, and the first switch is turned off and the second switch is turned on during a second time.