An organic light emitting diode (OLED) display includes a display unit including a plurality of pixels, a plurality of scan lines, and a plurality of data lines, a data driver transmitting a plurality of data signals to the plurality of data lines, a scan driver transmitting a plurality of scan signals to the plurality of scan lines, a compensation controller supplying a predetermined first current to each OLED in each of the plurality of pixels during a sensing period for measuring a driving voltage of the OLED for each of a plurality of pixels, receiving the driving voltage of the OLED supplied with the first current, and outputting measuring data for the transmitted driving voltage; and a signal controller compensating an input video signal according to the measuring data to generate image data. The compensation controller is separate from and external to the data driver.