The Hirshhorn Museum and Sculpture Garden in downtown Washington, D.C. is circular in shape without outside windows and with an inner open courtyard and fountain. The museum is operated as a part of the Smithsonian Institution. Three levels of galleries will be provided to exhibit paintings and sculptures. The structure presents special forming problems, chiefly because of an intricate grid of beams that supports the long span sections of the second floor. These beams are exposed to view from underneath and are designed in architecturally graceful shapes that are exceptionally difficult to cast. The pink granite aggregate concrete is used in forming these beams, which are approximately six feet thick. Deck and beam forms were supported not by shoring from below but by cables suspended from a steel I-beam above. Deck forms were of plastic coated plywood. Fiberglass-reinforced plastic forms were manufactured to a number of different configurations and each form was used four times. The center and outside forms were reused without modification. The inner forms were used for the first setting where the separation between the eccentric girders was the greatest. They were then cut progressively smaller for each successive use where the separation between rings became progressively less. Because the ring girders were laid out on true circles the angles and curves remained the same, even there the dimensions for the inner forms had to be altered by cutting. Forms were bolstered with each setting with heavy timbers nailed and bolted into place. In stripping, the forms were lighted by crane rather than removed from below.