It is the purpose of this chapter to provide standards for the functional properties of packaging systems used for solid oral dosage forms (SODFs) and liquid oral dosage forms (LODFs). The tests in this chapter may be applied to packaging systems for other dosage forms with the appropriate justification. These tests determine the moisture vapor transmission rate (MVTR) i.e., water vapor permeation rate, for plastic packaging systems for manufacturers, packagers, and repackagers (Table 1). This chapter also includes a classification system that allows pharmacists and institutional repackagers to select appropriate containers to repackage SODFs and LODFs. Definitions that apply to this classification system are provided in Packaging and Storage Requirements 〈659〉.