A discussion of the applicability of random sampling simulation to the problem of predicting "drift" failures. Drift failures are defined as system malfunctions occurring because the entire system, with its many interdependencies, performs at a level outside design limits. In particular, the study applies the Monte Carlo method to the problem of predicting system performance based on component performance data and subsystem or "black-box" performance data. The technique permits the integration into one model of all known stresses--environmental and operational--and other events affecting the system operation. Therefore, for a properly designed and executed Monte Carlo experiment at any level of aggregation, the derived performance estimates will be unbiased estimates of the actual system performance.