Visual applications need to represent, manipulate, store, and retrieve both raw and processed visual data. Existing relational and object-oriented database systems fail to offer satisfactory visual data management support because they lack the kinds of representations, storage structures, indices, access methods, and query mechanisms needed for visual data. We argue that extensible visual object stores offer feasible and effective means to address the data management needs of visual applications. ISR4 is such a visual object store under development at theUniversity ofMassachusetts for the management of persistent visual information. ISR4 is designed to offer extensive storage and retrieval support for complex and large visual data, customizable buffering and clustering, and spatial and temporal indexing, along with a variety of multi-dimensional access methods and query languages.