Аннотация:A large-scale survey of the physical condition of books and the nature of the collections in the Yale University Library system that evaluated more than 36,500 volumes was carried out.Results have been tabulated, compared by computer, and analyzed to provide statistical information on the fifteen distinct collections surveyed in thirty-six separate strata.Environmental conditions were also monitored.These studies, along with the analyses of binding materials and methods, were used to formulate probable reasons for deterioration levels as well as documenting these levels.Several questions of particular interest were compared in two-way intersections, and a brief analysis was made of publication dates in relation to age and condition of a selected group of books.It was found that 37.1 percent of the books sampled overall had brittle paper (i.e., broke after two double folds) and that 82.6 percent of the books overall had acidic paper (i.e., a pH of below 5.4).These and other results should help Yale and libraries elsewhere to identify their preservation needs and develop appropriate programs.