Strategic alliance between corporations is essential to build a CALS system. Specially, companies cooperate one another to accomplish the shared environment in the system. During the construction of the CALS system, we can apply the concepts of ILS and SCM to develop the breadth and depth of shared environment between firms. In order to build such intended environment in the CALS system, we propose five dimensions with 30 variables to be considered. These dimensions are Information Sharing, Task Sharing, System Sharing, Parts and Facilities Sharing, and Institution Sharing. Structured interviews were peformed to measure the degree of shared environment designed in 7 CALS pilot systems in Korea. The results show that the level of the shared environment in the context of vertical relationships between firms in the CALS systems is fairly high. In contrast, the level of the sharing between competing companies in horizontal relationships is relatively low in most of the pilot systems.