Nuclear power plants are not likely to be attacked but if they are, an attack would not have a major impact on energy supplies, although it would affect the industry's financial viability because cleanup costs would be substantial. Similarly, the major danger to the electrical power industry from terrorist attack results from the increase in operating expenses. However, the extensive transmission system is a weak link and could be destroyed. Liquid energy gases are vulnerable to sabotage, and their disruption would cause extensive and costly damage. The oil pipeline network is the most vulnerable industry because of American dependence on the pipeline to distribute oil and gas, the time required to repair damaged pipelines, and the ease of access to critical links in the system. Maps illustrate the major U.S. pipeline systems. Dissatisfied company employees have posed the greatest threat to the energy industry. Disrupting energy supplies is generally not a terrorist's objective but an end toward gaining more attention to a cause. Possible security countermeasures include controls over facility entry, employee security training, and separation of critical facilities. Tables, 24 reference notes, and a chronology of incidents at utility and oil company facilities between 1974 and May 1977 are included.