Mass-propagation of Yacon (Polymnia sonchifolia) was investigated by using the in vitro node culture method. Continuous axillary shoot formation was achieved by repeating node culture every 4-5 weeks in a MS medium supplemented with 0.1mg/l BA. Roots were formed from all the shoots within 2 weeks in this MS medium. Rooted plantlets were successfully established within 2 weeks in the porous soil medium under plastic cover. Thus, thousands of plants could be obtained in a year from a single shoot tip.