A real-time interactive distance lecture is a joint work that should be accomplished by the effort of the lecturer and his students in remote sites. It is important for the lecturer to get understanding information from the students which cannot be efficiently collected by only using video/audio channels between the lecturer and the students. This article proposes RIDEE-UIM (Understanding Information Management system for Real-time Interactive Distance Education Environment) for collecting understanding information from each participant to the lecturer during real time distance education activities. The usefulness of RIDEE-UIM has been confirmed by experiments. This article describes the basic idea, implementation and experiments of RIDEE-UIM. (Contains 9 figures.)