INTRODUCTIONIt is the purpose of this chapter to provide standards for the functional properties of packaging systems used for solid oral dosage forms (SODF) and liquid oral dosage forms (LODF) for pharmaceuticals and dietary supplements. Definitions that apply to this chapter are provided in Packaging and Storage Requirements á659ñ. The tests that follow are provided to determine the moisture vapor transmission rate (water vapor permeation rate) and spectral transmission of plastic containers. Test methods are provided to measure moisture vapor transmission rates that may be useful for pharmaceutical and dietary supplement manufacturers to determine the level of barrier protection provided by packaging systems for SODF. Additional methods are provided to determine classification of packaging systems for SODF and LODF that are repackaged by organizations or when being dispensed on prescription by pharmacists as single-unit and multiple-unit containers (Table 1). There may be additional packaging systems where the test methods in this section could be applied; however, any deviation should be described. If other methods are used to measure moisture vapor transmission rate, these methods should be described in sufficient detail to justify their use.