Abstract: A system and method of identifying outliers in item categories are described. A pairwise similarity measurement may be determined between each item listing in a plurality of item listings based on a comparison of at least one feature of each item listing. At least one outlier among the plurality of item listings may be determined using the pairwise similarity measurements. The feature(s) may comprise at least one feature from a group of features consisting of: a title, an image, a price, an attribute, and a description. Each item listing in the plurality of item listings may belong to the same leaf or non-leaf category in a network-based marketplace or publication system. The outlier(s) may be determined using at least one clustering algorithm. The clustering algorithm(s) may comprise an agglomerative hierarchical clustering algorithm and/or a density-based clustering algorithm.