Within the frame of the research program "Parallel and Distributed Systems", in the period 1999-2003, the following important results have been reached: A new type of regular interconnection topology, d-mesh, has been proposed. It provides shorter node-to-node distances. Simulation results show that the proposed topology is among the best known from this field, from the point of view of communication complexity and also price performance. Two papers have been published from this area in international journals. A patent, describing the method for the interconnection of neighbouring nodes in d-mesh was acquired. Multipart communication is one of the crucial factor in the final performance of any parallel computing system. If the communication method is not optimal, then the whole parallel algorithm might remain inefficient. New methods of collective communication pattern one-to-one, one-to-all and all-to-all have been investigated for different interconnection topologies, including mesh and torous. New theoretical results obtained have been published in three international papers. Parallel simulation program has been implemented for simulating physical phenomena in biomedicine. Mathematical model is based on the partial differential equations, that are solved numerically by parallel programs. As an example, a simulation of topical heart cooling was implemented in detail on the parallel computer. Heat transfer and fluid flow were included into the model in order to simulate the topical cooling by a cold solution circulating around the heart. Simulation results have to be evaluated by real measurements. Therefore we designed a device and methods for measurements of biomedical signals including temperatures, electric potential, small forces, etc. We published 6 papers from this area, besides, a special issue of the international journal "Computers in Biology and Medicine", with co-editing by a member of our program was published in 2003. Secure and reliable computer systems have been also investigated within the scope of broader information systems. Human factor was identified as one of the most important. Quantitative methods were used for its modelling and evaluation. Several new theoretical results have been obtained in the area of formalization of security policies (4 published papers). Our research results have been discussed and presented, beside publications, also to wider public on international conferences, by cooperation in several international consortia for EU projects, and by invited or visiting lectures on foreign universities.