This book constitutes the refereed proceedings of the 4th European Symposium on Research in Computer Security, ESORICS '96, held in Rome, Italy, in September 1996 in conjunction with the 1996 Italian National Computer Conference, AICA '96. The 21 revised full papers presented in the book were carefully selected from 58 submissions. They are organized in sections on electronic commerce, advanced access control models for database systems, distributed systems, security issues for mobile computing, network security, theoretical foundations of security, and secure database architectures.