Cerebellar Purkinje cells are key elements regulating motor learning and motor coordination. Gene transfer into neurons, followed by the assessment of the effects on neural function, is an effective approach for examining gene function. However, this method has not been used fully in the study of the cerebellum, because of the obstacle of delivering genes into Purkinje cells. To overcome this, we used a human immunodeficiency virus (HIV)-derived lentiviral vector and examined the transduction profile of the vector in the cerebellum. A lentiviral vector expressing GFP was injected into the cerebellar cortex. Seven days after the injection, GFP was predominantly expressed in Purkinje cells. GFP was also expressed, though less efficiently, in other cortical interneurons and Bergmann glias. In contrast to reported findings with other viral vectors, no transduced cells were observed outside of the cerebellar cortex, even in the deep cerebellar nuclei, pontine nuclei and inferior olivary complex, which are synaptically linked with Purkinje cells or granule cells. Thus, when HIV-derived lentiviral vectors were injected into the cerebellar cortex, transduction was limited to the cells in the cerebellar cortex, with the highest tropism for Purkinje cells. These results suggest that HIV-derived lentiviral vectors are useful for the study of gene function in Purkinje cells as well as for application as a gene therapy tool for the treatment of diseases that affect Purkinje cells. [J Physiol Sci. 2006;56 Suppl:S167]