An organic light emitting display comprising: a plurality of pixels, each pixel including an organic light emitting diode OLED; a plurality of sense lines respectively connected to the pixels; a sense line driver for driving the sense lines; a sensing unit for extracting information corresponding to a degradation level of the organic light emitting diodes provided in each of the pixels; a storage unit for storing the information obtained by the sensing unit, calculating degradation level information of the organic light emitting diodes using the stored information, and storing the degradation level information; a conversion unit for converting input data into correction data using the degradation level information stored in the storage unit; and a data driver to receive the correction data output from the conversion unit and to generate data signals to be supplied to the plurality of pixels via respective data lines; wherein the sense line driver is arranged to drive the sense lines to selectively connect each of the pixels to a respective data line for a predetermined period; and the sensing unit is arranged to provide first and second reference currents to the respective data lines and to measure first and second voltages corresponding to the reference currents during the predetermined period, the first and second voltages including the information corresponding to the degradation level of the organic light emitting diodes provided in each of the pixels, wherein the sensing unit includes a sensing circuit and the sensing circuit comprises: a first current source unit arranged to supply the first reference current into the organic light emitting diode provided in each of the pixels; a second current source unit arranged to supply the second reference current into the organic light emitting diode provided in each of the pixels; and first and second switching elements (SW1 and SW2) coupled respectively to the first and second current source units, wherein each of the pixels comprises: a first transistor for receiving data from one of the data lines Dm and transmitting the data to a driving transistor for driving the organic light emitting diode when a scan line Sn connected to the gate of the first transistor turns the first transistor on; and a third transistor for coupling the data line (Dm) to the organic light emitting diode to provide the first and the second reference currents to the light emitting diode when the corresponding sense line CLn connected to the gate of the third transistor turns the third transistor on. a plurality of pixels, each pixel including an organic light emitting diode OLED; a plurality of sense lines respectively connected to the pixels; a sense line driver for driving the sense lines; a sensing unit for extracting information corresponding to a degradation level of the organic light emitting diodes provided in each of the pixels; a storage unit for storing the information obtained by the sensing unit, calculating degradation level information of the organic light emitting diodes using the stored information, and storing the degradation level information; a conversion unit for converting input data into correction data using the degradation level information stored in the storage unit; and a data driver to receive the correction data output from the conversion unit and to generate data signals to be supplied to the plurality of pixels via respective data lines; wherein the sense line driver is arranged to drive the sense lines to selectively connect each of the pixels to a respective data line for a predetermined period; and the sensing unit is arranged to provide first and second reference currents to the respective data lines and to measure first and second voltages corresponding to the reference currents during the predetermined period, the first and second voltages including the information corresponding to the degradation level of the organic light emitting diodes provided in each of the pixels, wherein the sensing unit includes a sensing circuit and the sensing circuit comprises: a first current source unit arranged to supply the first reference current into the organic light emitting diode provided in each of the pixels; a second current source unit arranged to supply the second reference current into the organic light emitting diode provided in each of the pixels; and first and second switching elements (SW1 and SW2) coupled respectively to the first and second current source units, a first current source unit arranged to supply the first reference current into the organic light emitting diode provided in each of the pixels; a second current source unit arranged to supply the second reference current into the organic light emitting diode provided in each of the pixels; and first and second switching elements (SW1 and SW2) coupled respectively to the first and second current source units, a first transistor for receiving data from one of the data lines Dm and transmitting the data to a driving transistor for driving the organic light emitting diode when a scan line Sn connected to the gate of the first transistor turns the first transistor on; and a third transistor for coupling the data line (Dm) to the organic light emitting diode to provide the first and the second reference currents to the light emitting diode when the corresponding sense line CLn connected to the gate of the third transistor turns the third transistor on.