The method chosen to eradicate the insects and prevent a recurrence of the infestation had to be non-toxic to humans, not harmful to the materials, not disruptive of service to the library's readers, and economically feasible. This was the first use of the deep-freezing technique by a library or archive to deal with this problem, and it continues to be used at Yale as a preventive measure in the processing of new acquisitions. The Beinecke Library has twenty-six miles of bookshelves (mostly underground) with filtered air-conditioning constantly controlling temperature and humidity at 21° ± 3°C (70° ± 5°F) and 50° ± 5% R.H. The infestation occurred in two adjacent underground bookstacks and involved two kinds of material: printed books (chiefly vellum-bound) in one area and leather-bound, Near Eastern manuscripts in the other. Proposed standard fumigation techniques employing lethal gases, crystalline fumigants, or chemical fluid were rejected in favor of deep-freezing, a technique developed at Yale over several years to collect entomological specimens. As the technique exterminates all insects, it is as effective as any chemical fumigation. Additionally, deep-freezing appealed because it could be executed within the confines of the library and would be least disruptive to normal library operations. The paper concludes with a detailed description of the Library's deep-freezing program. The equipment includes: a standard walk-in blast freezer which has electric fans behind its freezing coils; a 24 hour, 7 day graph temperature recorder; a monitor meter with thermocouple leads to check interior temperature of the books.