This is a comparative study of oxygen permeation and microbial ingress into a drug vial stopper that is an elastomeric pharmaceutical compound versus the same compound coated with a thin Teflon-type film coating. The objective of this study is to determine if the film coating causes any changes in the rate of oxygen permeation or microbial ingress into the vial from the environment. From the data obtained it is concluded that the film did not change either the oxygen or microbial ingress into the vial; therefore the stoppers are essentially equivalent with respect to these parameters.