Abstract: The invention relates to a monitored burn-in system for operating a group of semiconductor devices such as ICs under an accelerated aging condition. To automatically and appropriately determine the burn-in duration, the disclosed system includes a counting means to count a cumulative number of failed devices at predetermined time intervals, a computing means to compute a cumulative failure rate of the devices at the same time intervals and further compute an increment of the cumulative failure rate during each of the time intervals, and a comparison and control means to compare the computed increment of the cumulative failure rate with a predetermined reference increment of cumulative failure rate and produce a command signal to terminate the burn-in procedure when the computed increment is not greater than the reference increment.