The latest video coding standard H.264/AVC outperforms previous standards in terms of coding efficiency at cost of higher runtime complexity. When RDO is used, the most time-consuming process in a H.264/AVC encoder is mode decision, where all the intra/inter modes are tested to find the optimal coding mode. In this paper, we present a fast intra mode decision scheme, which first detects the texture direction and only tests a subset of intra modes consistent with detected direction. Experimental results demonstrate that the proposed scheme significantly reduces the overall encoding time with negligible coding performance loss.