The European Pharmacopeia (Ph. Eur.) hydrolytic resistance method for glass vials is routinely used to screen pharmaceutical glass vial supply. Due to reliance on this method to reduce the risk of glass vial delamination in pharmaceutical drug products, it is important that the sources of method variability be understood and controlled. Several potential sources of variability in the Ph. Eur. alkalinity method have been studied for 3cc glass vials. Method parameters including vial rinsing, fill volume determination, vial covering, autoclave cycle execution, sample hold times, and titration procedure were evaluated in this study. The results of this study indicate the method parameters which require stringent control in order to achieve acceptable method precision and robustness.