Spin injection/detection and coherent spin transport are key ingredients in Spintronics, which were first demonstrated in the giant magnetoresistance or GMR effect in all-metal systems. In this talk, I will present our recent progress using organic semiconductors. In spin valves consisting of two ferromagnetic layers (La2/3Sr1/3MnO3 or LSMO and Co) and an organic semiconductor spacer (Alq3), we have successfully shown electrical spin injection/detection and coherent spin transport through the GMR effect. In addition, we have also found a high-field magnetoresistance effect in these structures. Our work shows that this high field effect originates from the magnetic field enhanced carrier injection due to the anomalous Fermi level shift in double exchange ferromagnets such as LSMO.