A fast feature-based intra/inter coding mode selection scheme for the H.264/AVC video coding standard is proposed in this paper. First, three features are extracted from a macroblock to form a feature space. Then, the feature space is partitioned into three regions, i.e., risk-free, risk-tolerable, and risk-intolerable regions, where the risk is calculated using the rate-distortion (RD) performance loss due to wrong mode decision as well as the probability distribution of inter/intra modes in the feature space obtained from an off-line training process. Depending on the region where the feature vector of a macroblock is located, we can apply mechanisms of different complexity for final mode decision. To calculate the likelihood function of the risk, both parametric and nonparametric density estimation schemes are developed to offer different rate-distortion–complexity tradeoffs. It is demonstrated by experimental results that the proposed algorithm can save approximately 20%–32% of the total encoding time of H.264 (JM7.3a) with little degradation in the rate-distortion performance.