This volume contains the proceedings of the 13th Italian Workshop on Neural Nets WIRN VIETRI 2002, jointly organized by the International Institute for Advanced Scienti?c Studies "Eduardo R. Caianiello" (IIASS), the Societ'aIt- iana Reti Neuroniche (SIREN), the IEEE NNC Italian RIG, and the Italian SIG of the INNS. In this book a review talk, dealing with a very up-to-date topic "Ensembles of Learning Machines", and original contributions, approved by the referee c- mittee as oral or poster presentations, have been collected. The contributions have been assembled, for reading convenience, into sections. The last section, devoted to "Learning in Neural Networks: Limitations and Future Trends",wasorganizedbyProf.M. Goriandalsocontainstheinvitedl- ture "Mathematical Modeling of Generalization" given by Dr. Martin Anthony. The ?rst and second sections are dedicated, respectively, to the memory of two scientists who were friends in life, Professors Francesco Lauria and Eduardo R. Caianiello. The editors thank all the participants for their quali?ed contributions, while special thanks go to Prof. M. Gori for his help in the organization, and to the referees for their accurate work. July 2002 MariaMarinaro RobertoTagliaferri Organizing-Scienti?cCommittee B. Apolloni (Univ. Milano), A. Bertoni (Univ. Milano), N. A. Borghese (Univ. Milano), D. D. Caviglia (Univ. Genova), P. Campadelli (Univ. Milano), A. Chella (Univ. Palermo), A. Colla (ELSAG Genova), A. Esposito (I.I.A.S.S.), C.