PrefaceThis volume reports the proceedings of the 16th Italian Workshop on Neural Nets WIRN 2005 and the satellite International Workshop on Natural and Artificial Immune Systems NAIS 2005. The workshops, held in Vietri sul Mare (SA) from 8 to 11 June, were jointly organized by the International Institute for Advanced Scientific Studies "Eduardo R. Caianiello" (IIASS) and the Società Italiana Reti Neuroniche (SIREN). The new format of the SIREN annual meeting-WIRN plus satellite conference-stems from the aim of sharing neural network methodologies with close research communities. The goal this year was to recognize and exploit a commonality of subsymbolic methods used both in neural networks and immune system research to study complex systems with a distinguishing common feature. All these systems are indeed constituted by a mass of elementary organisms/computational units generating ensemble functionalities, such as optimization and learning, denoting traits of intelligent thought. Moreover, like neural networks, the area of natural and artificial immune systems is also developing in response to needs for a mix of inter-and multidisciplinary expertise, spanning immunology, biology, mathematics, computer science, and medicine, among others, having rebounding of models and results from biological to computational realms and vice versa as a great strength point.The volume contains invited review papers and selected original contributions presented in oral or poster sessions by both Italian and foreign researchers. The contributions have been assembled, for reading convenience, into eight sections. The first section reports the lecture given by the winner of the Premio Caianiello award. Sections II to V contain wide-spectrum papers on neural networks, split in four parts; models, architectures and algorithms, signal processing, and pattern recognition, respectively. The sixth section focuses on methodologies and applications of fuzzy and neurofuzzy computing promoted by a joint Spanish-Italian working group. The last two sections gather papers on immune systems divided into natural systems and artificial systems.The editors would like to thank the invited speakers and all the contributors whose highly qualified papers helped the success of the workshops. Finally, special thanks go to the referees for their accurate work.