Frozen sections are performed for the purpose of rapid diagnosis while a patient is undergoing surgery, usually under general anesthesia, as a basis for making immediate treatment decisions. Therefore, frozen section diagnosis is often a highly demanding situation for the pathologist who must render a diagnosis quickly and a crucial determination for the patient and surgeon. In addition to the need for rapid recall of differential diagnoses, there are many pitfalls and artifacts that add to the risk of frozen section diagnosis that are not present with permanent sections of fully processed tissues that can be examined in a more leisurely fashion. Most standard pathology textbooks, both general and subspecialty, largely ignore the topic of frozen section. Few textbooks have ever focused exclusively on frozen section diagnosis and those textbooks that have done so are now out-of-date and have limited numbers of black and white figures. None has emphasized the education of the surgeon in terms of frozen section benefits, limitations or proper utilization. The Frozen Section Library series will provide convenient, user-friendly handbooks for each organ system to expedite use in the hurried frozen section situation. These books will be small and light-weight, copiously color illustrated with images of actual frozen sections, highlighting pitfalls, artifacts and differential diagnosis. These books will also include perspectives for the surgeon and for communication with the surgeon and suggest ancillary procedures (for example, when to take tissue for microbiology cultures). Each 5 X 8 book is estimated to be about 200 to 250 pages in toto with 100 to 150 color figures each. As a handbook for practicing pathologists, these books will be indispensable aids to diagnosis and avoiding dangers in one of the most challenging situations that pathologists encounter. Problems, such as differentiation of benign processes from malignant neoplasms which may be more difficult on frozen section than permanent section and which have a serious impact on the surgeon's immediate treatment decisions, will be emphasized. Rapid consideration of differential diagnoses and how to avoid traps caused by frozen section artifacts will be readily accessible to the users of the handbooks. A series of concise, easy-to-use, well-illustrated handbooks alleviates the often frustrating and time-consuming, sometimes futile, process of searching through bulky textbooks that are unlikely to illustrate or discuss pathologic diagnoses from the perspective of frozen sections in the first place. Tables and charts will provide guidance for differential diagnosis of various histologic patterns. The advantages of a series of organ-specific handbooks, in addition to the ease-of-use and manageable size, is that (1) it allows more comprehensive coverage of more diagnoses, both common and rare, than a single volume that tries to highlight a limited number of diagnoses for each organ and (2) it allows more detailed insight by permitting experienced authorities to emphasize the peculiarities of frozen section for each organ system. Although some differences in practice of frozen section exist between different institutions, such as differing policies regarding whether or not to perform frozen section on specific types of specimens, these differences are generally not significant and can be discussed ( an organ-specific handbook by an expert in that organ system permits more opportunity for this type of discussion). Touch preparations, which are used for some organs such as central nervous system or thyroid more often than others, will be appropriately emphasized and illustrated according to the need for each specific organ. This series will be highly valuable to practicing surgical pathologists, both community and academic, and to pathology residents and fellows. The perspectives provided will also be valuable to surgeons and especially to surgery residents and fellows who must answer questions about pathology and frozen section on their board examinations. These handbooks will be easily portable by the individual but it is envisioned that many departments will want to also keep a series readily available in the frozen section laboratory.