This book promotes an interdisciplinary approach to maintenance, through the presentation of practical and theoretical research in the field of electrical, civil, and mechanical engineering. The goal is to raise the level of maintenance knowledge, taking into account the continuous advancement of engineering and technology in all spheres of economy, infrastructure, and public services. This book contains papers presented at the 30th International Conference on Organization and Technology of Maintenance (OTO 2021), and the conference was held on Josip Juraj Strossmayer University of Osijek, Faculty of Electrical Engineering, Computer Science and Information Technology Osijek on 10-11 December 2021. The book brings 36 original papers written by authors from ten countries that underwent a blind review process by the international review board members. The conference covers the topics as organization and management of maintenance, maintenance technologies, quality management in system maintenance, information systems in maintenance, product lifecycle management, design for maintainability, material and structure properties, reliability of technical systems and environmental safety, diagnosis and prognosis of failures and operational malfunctions, design optimization for maintenance, maintenance in technical systems, analysis of efficiency and cost effectiveness of maintenance, influence of maintenance on the environment and employee safety, maintenance legislation, and education for maintenance. The papers presented in the book reflect the current state of approach to maintenance as an interdisciplinary field. The OTO conference proved itself as an ideal opportunity for communication between scientists and experts in maintenance practice with the aim to raise the level of expertise and introduce new methods and maintenance procedures into everyday practice.