A new support vector clustering (SVC)-based probabilistic approach is developed for unsupervised chemical process monitoring and fault classification in this article. The spherical centers and radii of different clusters corresponding to normal and various kinds of faulty operations are estimated in the kernel feature space. Then the geometric distance of the monitored samples to different cluster centers and boundary support vectors are computed so that the distance-ratio-based probabilistic-like index can be further defined. Thus, the most probable clusters can be assigned to the monitored samples for fault detection and classification. The proposed SVC monitoring approach is applied to two test scenarios in the Tennessee Eastman Chemical process and its results are compared to those of the conventional K-nearest neighbor Fisher discriminant analysis (KNN-FDA) and K-nearest neighbor support vector machine (KNN-SVM) methods. The result comparison demonstrates the superiority of the SVC-based probabilistic approach over the traditional KNN-FDA and KNN-SVM methods in terms of fault detection and classification accuracies. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 407-419, 2013