"The purpose of this paper is to clarify by objective time_based notation how an environment which changes with time influence behavior. More particularly, this research deals with how behavior in the meeting place is affected by both time and the physical environment. At two popular meeting places in downtown Tokyo, a person's motion was recorded by three TV cameras set in different positions. The movement of each person who answered our interview after rendezvous was studied on the video tape. Items of interview included promised time to meet, description used to specify meeting place, and the experiences of using the place, which we call "initial information Based on observation of physical arrangements and people's distribution, several contour maps were created to show the level of local potential" in the meeting place for three basic desires: comfortableness (refuge), easiness to find (prospect), easiness to be found (retreat /reveal). The person's movement ti_ace was overlaid on these maps to see the changes of the level of potential before and after each movement. Thus a time_based notation was used to describe a series of position choices which reflect varying mental states, or the priority of three basic desires. An analysis of behavior using the notation revealed that, (1) such initial information as specified position and expected direction of approach influence behavior while waiting; (2) different spatial arrangement of the meeting place influences position choice for having good visibility; (3) in crowded situations the desire to be found seem to be growing as time passed. Finally, we proposed implications for the design of meeting places considering temporal, spatial and psychological factors."