In this paper, we present a solution to the problem of dynamically deploying grid service factories onto computing nodes running an implementation of the Open Grid Services Infrastructure (OGSI). By providing a non-intrusive Hot Deployment Service (HDS), we extend the service-oriented grid computing paradigm, as it is defined by the Open Grid Services Architecture (OGSA), to provide a more dynamic ad hoc grid environment. Service-oriented grid middleware utilizing the HDS enables organizations or interorganizational communities to form an ad hoc grid to harness unused and scattered resources of an existing IT-infrastructure. The availability of the HDS also improves the capabilities to manage existing grid systems based on the Globus Toolkit 3, which is a vital requirement for the adoption of serviceoriented grid systems in production environments. Categories and Subject Descriptors H.3.5 [Information Systems]: Information Storage And Retrieval—Web-based services; C.2.4 [Computer S...