This document outlines principles for preserving library materials and developing a preservation policy. It discusses threats to materials like natural deterioration, environmental conditions, and handling practices. A preservation assessment should identify risks, evaluate the physical state of materials and facilities, and be done in consultation with all library departments. The goals are to understand preservation needs, prioritize major threats, and make recommendations to care for collections given available resources. Surveys of buildings, disaster plans, environments, and collections can provide needed information to create a preservation policy.