Ingredients necessary for studying the effects of environmental interactions are presented. A technique for quantitatively predicting the effects of combined environments upon components was developed and applied to test data obtained under controlled conditions. The synergistic effects were equalized as to exposure time and the number of environmental encounters. The data was then statistically analyzed with the following conclusions: 1. Combined environments produce a synergistic effect which acts to reduce the over-all stress severity imposed upon components by the individual environments. 2. The length of time parts are exposed to a combined environment is more critical to component life than the number of encounters with that environment. 3. Combined environments appear to produce the same effect upon a given component irrespective of the environments concerned in the combination. 4. Different components are affected in different ways by a given combined environment.