The papers presented on this occasion examined the most significant aspects of diagnostic strategies, emphasizing the importance of predictive maintenance in reducing production shortages and the costs of plant management. The contributions of these authors allow a critical comparison of the varied experiences in developing and applying the different diagnostic methodologies employed in several parts of the world. The following problems are discussed: characteristics of condition monitoring systems - data acquisition techniques and data processing methodologies; choice of transducers and of measurement point locations; data compression techniques; alarm levels evaluation (acceptance regions); strategies for detecting malfunction conditions; diagnostic methodologies for the on-line and off-line identification of