Accelerated life tests (ALTs) are aimed at revealing and understanding the physics of the expected or occurred failures, i.e., are able to detect the possible failure modes and mechanisms. Another objective of the ALTs is to accumulate representative failure statistics. Adequately designed, carefully conducted, and properly interpreted ALTs provide a consistent basis for obtaining the ultimate information of the reliability of a product—the predicted probability of failure after the given time of service in the given conditions. Such tests can dramatically facilitate the solution to the cost effectiveness and time-to-market problems. ALTs should play an important role in the evaluation, prediction and assurance of the reliability of microelectronics and optoelectronics devices and systems. In the majority of cases, ALTs should be conducted in addition to the qualification tests required by the existing standards. There might also be situations when ALTs can be (and, probably, should be) used as an effective substitution for such standards, or, at least, as the basis for the improvement of the existing qualification specifications. We describe different types (categories) of accelerated tests, with an emphasis on the role that ALTs should play in the development, design, qualification, and manufacturing of microelectronics and photonics products. We discuss the challenges associated with the implementation and use of the ALTs, potential pitfalls (primarily those associated with possible “shifts” in the mechanisms and modes of failure), and the interaction of the ALTs with other types of accelerated tests. The role of the nondestructive evaluations is also briefly outlined. The case of a laser welded optoelectronic package assembly is used to illustrate some concepts addressed. “All life is an experiment. The more experiments you make the better” Ralph Waldo Emerson “In the long run we are all dead” John Maynard Keynes