This paper presents a fast cone beam reconstruction method accelerated on the graphics processing unit (GPU). We implement the Feldkamp, Davis, and Kress (FDK) algorithm on the OpenGL graphics pipeline, which allows us to exploit the full resources and capabilities available on the GPU. The proposed method differs from previous GPU-based methods in having an RGBA packing scheme capable of directly dealing with projections without rebinning. It also reduces the amount of computation by using a data reuse scheme, which is useful to save the memory bandwidth for this memory-intensive problem. Both schemes contribute to reduce the number of rendering passes, namely the number of kernel invocations on the GPU, realizing fast cone beam reconstruction. We show some experimental results obtained on a desktop PC with an nVIDIA GeForce 8800 GTX card. As a result, the proposed method takes 8.1 seconds to reconstruct a 512<sup>3</sup>-voxel volume from 360 512<sup>2</sup>-pixel projection images. This execution time is equivalent to a 15.6-fold speedup over a CPU implementation, showing 10% higher performance as compared with a previous OpenGL-based method that requires the single-slice rebinning of projections for acceleration. With respect to non-rebinned data, our method provides approximately three times higher performance than the previous method.