A pixel circuit for an organic light emitting display includes first, second, third, fourth, fifth, and sixth MOS transistors, a first capacitor, and an organic light emitting diode. The gate electrode of the first MOS transistor receives a first scanning signal. The first electrode of the first MOS transistor receives a data signal. The gate electrode of the third MOS transistor receives a control signal. The gate electrode of the fourth MOS transistor receives the first scanning signal. The gate electrode of the fifth MOS transistor receives the control signal. The first electrode of the fifth MOS transistor receives a reference voltage. The gate electrode of the sixth MOS transistor receives a second scanning signal. The first electrode of the sixth MOS transistor receives the reference voltage.