Abstract: A process for the burn-in of either or both analog and digital integrated circuits where the various functions in the individual circuits are tested continuously and individually, while the circuits are cyclically caused to work at extreme temperatures, and the test is stopped when a predetermined error rate has been reached. To perform the process, a circuit board comprises, in addition to the circuits tested at intermittent elevated temperatures, also auxiliary circuits for data collection and data compaction, said circuits being present at a constant normal working temperature during the burn-in sequence.