The report covers work performed during the period September 1, 1959 through September 30, 1959. The general objectives of the program of "Studies of Reactor Containment" are to accomplish theoretical and experimental investigations of the loads to which external containment structures for nuclear reactors are subjected in the vent of a violent incident at the reactor core, the evaluation of methods of reducing that loading, and the study of the response of and design criteria for external containment structures as a result of such loading. Progress of technical effort during the report period is summarized for each of the eight tasks of the program.