In this chapter, we discuss issues related to ehealth and focus on two major challenges in distributed healthcare database management: database heterogeneity and user mobility. We designed and prototyped a mobile-agent-based mobile data-access system framework that can address these challenges. It applies a thesaurus- based hierarchical database federation to cope with database heterogeneity and utilizes the mobile-agent technology to respond to the complications introduced by user mobility and wireless networks. The functions provided by this system are described in detail and a performance evaluation is also provided.