The Smithsonian Institution has over 10 million photographs in some 2,500 collections belonging to dozens of its separate museums and bureaus. Management of such a vast assortment of material has been spearheaded by the Smithsonian Institution Archives, which itself controls over 250,000 photographs. One collection of particular importance, consisting of over 15,000 photographs by C. M. Bell, Mathew Brady, Peter A. Juley, etc., is extensively used in exhibitions and publications on topics ranging from the history of science in the United States to the history of American museums. This collection was recently surveyed for condition and conservation treatment, during which time a number of interesting deterioration problems were discovered and objects were selected for analysis and treatment. The author focuses on the importance and diverse nature of the Smithsonian's collection, the survey technique and strategy, the composition and analysis of some unusual components of the photographs, distinctive degradation problems, and the treatment of several examples. Case studies focus on the use of poulticing in the treatment of coated photographs, and the use of goldbeater's skin, parchment size, and Japanese paper in the repair of a cased (leather) photograph.