A process by which components or assemblies are tested at the extremes of their normal operating conditions, usually in terms of temperature and voltage limits, for a period of hours or days in order to detect early life defects. It is not meant to be a destructive test.

Environmental stress screening (ESS) refers to the process of exposing a newly manufactured product or component (typically electronic) to stresses such as thermal cycling and vibration in order to force latent defects to manifest themselves by failure during the screening process. The survivng population, upon completion of screening, can be assumed to have a higher reliability than a similar unscreened population.