Adeno-associated virus (AAV) is a non-pathogenic, replication defective parvovirus. In the absence of helper adenovirus, AAV stably integrates into a defined region of human chromosome 19. Because of these unique properties, recombinant AAV is considered to be an attractive vector for human gene therapy. It has been demonstrated that AAV vectors are capable of efficient transduction of various types of cells including hematopoietic cells and post mitotic neuronal cells. We have recently developed a new strategy for large scale preparation of high titer AAV vectors by using packaging cell lines and sulfonated cellulose column chromatography. This new strategy may be important for further development of gene therapy using AAV vectors.