Despite the best of engineering practices that rely on reliability, human factors, and continuous quality improvement, severe accidents involving complex technological systems occur regularly: bridges collapse, chemical plants catch fire and explode, airplanes crash, and nuclear reactors melt down. The most comprehensive approach to understanding the causes of such disasters is based on systems engineering that highlights the limits of traditional event-chain models of accident causation. The course focuses on this approach using a group project but also provides an overview of the various sociological theories that have attempted to elucidate the organizational and psychological factors underlying the failure of sociotechnical systems.