It is difficult to extract tacit knowledge in the workplace. In this paper, we apply video annotation to externalize the technologies and skills in plant operations. We have developed two prototype systems. The first is an interactive support system using multimedia, which offers functions for collecting "know-how" and "know-why" from on-site plant operations and for presenting this information as learning materials. The second is a system for evaluating emergency training results and for extracting common problems and lesson points. This system is useful for exploratory sequential data analysis of human behavior.