When a rat treated with amphetamine (0.5-5 mg/kg) locomotes in an unfamiliar environment, there are one or two places which it visits most often. In these one or two places the mean duration of a visit (stop) is the longest, and, compared to other places, the incidence of grooming and rearing are the highest. Since in intact rats these features of place characterize it as a 'home base', it is concluded that under amphetamine rats also establish one or two home bases. One home base was generally established by rats treated with low doses of amphetamine, while two bases were most evident in those treated with high doses. Since the paths of locomotion in amphetamine-treated rats were previously described to be stereotyped, it is suggested that home base location under this drug may be used as a reference point in the assessment of the organization of stereotyped locomotor behavior.