In this chapter, we present PUB.MAS, a multiagent system able to retrieve and categorize bioinformatics publications from selected Web sources. The chapter extends and revises our previous work (Armano et al., 2007). The main extensions consist of a more detailed presentation of the information extraction task, a deep explanation of the adopted hierarchical text categorization technique, and the description of the prototype that has been implemented. Built upon X.MAS (Addis et al., 2008), a generic multiagent architecture aimed at retrieving, filtering and reorganizing information according to user interests, PUB.MAS is able to: (i) extract information from online digital archives; (ii) categorize publications according to a given taxonomy; and (iii) process user's feedback. As for information extraction, PUB.MAS provides specific wrappers able to extract publications from RSS-based Web pages and from Web Services. As for categorization, PUB.MAS performs Progressive Filtering (PF), the effective hierarchical text categorization technique described in (Addis et al., 2010). In its simplest setting, PF decomposes a given rooted taxonomy into pipelines, one for each existing path between the root and each node of the taxonomy, so that each pipeline can be tuned in isolation. To this end, a threshold selection algorithm has been devised, aimed at finding a sub-optimal combination of thresholds for each pipeline. PUB.MAS provides also suitable strategies to allow users to express what they are really interested in and to personalize search results accordingly. Moreover, PUB.MAS provides a straightforward approach to user feedback with the goal of improving the performance of the system depending on user needs and preferences. The prototype allows users to set the sources from which publications will be extracted and the topics s/he is interested in. As for the digital archives, the user can choose between BMC Bioinformatics and PubMed Central. As for the topics of interest, the user can select one or more categories from the adopted taxonomy, which is taken from the TAMBIS ontology (Baker et al., 1999). The overall task begins with agents able to handle the selected digital archives, which extract the candidate publications. Then, all agents that embody a classifier trained on the selected topics are involved to perform text categorization. Finally, the system supplies the user with the selected publications through suitable interface agents. The chapter is organized as follows. First, we give a brief survey of relevant related work on: (i) scientific publication retrieval; (ii) hierarchical text categorization; and (iii) multiagent systems in information retrieval. Subsequently, we concentrate on the task of retrieving and categorizing bioinformatics publications. Then, PUB.MAS is illustrated together with its performances and the implemented prototype. Conclusions end the chapter.