It is an increased interest in the therapeutic potential of Cannabis sativa L. (marijuana) for treatment of multiple sclerosis and HIV neuropathy. Because of limitation in cultivation of this plant, an efficient hairy root induction system for Cannabis sativa L. was developed in the present study. Agrobacterium rhizogenes mediated transformation performed by two different co-cultivation mediums and four different bacterial strains including A4, ATCC15834, MSU440, and A13 (MAFF-02-10266). Genomic DNA from putative transgenic hairy root lines and the control root was extracted using a modified CTAB protocol. Molecular analysis of transformed root lines was confirmed by polymerase chain reaction using specific primers of the rolB gene. The transformation frequency by Murashige and Skoog co-cultivation medium resulting in hairy root induction frequencies of 42.3%, 46.3%, 68.6% and 39.3% by A4, ATCC15834, MSU440, and A13 strains, respectively. There was no significant difference between MS or ½ MS co-cultivation mediums.  This study established a reliable protocol for induction of hairy roots of C. sativa. The best A. rhisogenes strain was MSU440. It was observed no significant difference between MS and ½ MS co-cultivation mediums on transformation frequency.