In health care practice, diagnosis and therapy tasks are founded on the analysis of medical images. Traditionally, such analysis was performed using optical devices like light boxes or microscopes installed in clinical rooms or laboratories. In the last decade, personal computers have revolutioned this practice and today medical imaging is based on soft-copies of image material rather than films or specimens. Acquisition, storage and display of medical images are performed through digital computers and/or workstations. More recently, the introduction of networked computers has lead to the concept of telemedicine, that is making available remote medical facilities through the use of personal computers and digital networks. In this document we analyse the problem of real-time performance in telemedicine applications and we propose a new architecture that allows the interactive and real-time exchange of medical images. This architecture is based on a hierarchical database to store images, an high-speed network to transmit images and a navigation module allowing the user to dynamically select the portion and resolution of the images under inspection. In the second part of the document we describe, in particular, the prototype developed according to the described architecture and we discuss performance and optimization aspects.