This tutorial discusses test methods and voltage stress approaches required to ensure effective cost effective defect screening to produce high quality, reliable products. Wafer level reliability screens (WLRS) refers to the application of screens during wafer test that will both activate and detect a sufficient number of defects so that early life failure rate (ELFR) is reduced enough to meet customer spec, preferably without doing burn-in. Further, these screens have to have acceptable yield loss and acceptable test times.