When rats are placed in a novel environment, they alternate between progression and stopping: in the course of a session they stop briefly in many places, but in one or two places they also stop for very long periods. The place in which they stay for the longest cumulative time is defined as the rat's home base. In this place the incidences of grooming and of rearing are high and often the highest. In addition, the number of visits to the home base is typically the highest. Some rats establish a secondary base with similar properties to those of the main home base. The location of the base influences the mode of progression throughout the environment: progression away from base is slower and includes more stops than progression back. It is suggested that this paradigm may be used for the analysis of the spatial organization of locomotor behavior in neuroscience research.