A vertical, rotatory liquid culture system was developed for the mass-production of hybrid rice (Oryza sativa L.) by multiplying axillary shoots. Multiple shoots were induced by a combination of cytokinin (10-5 or 10-4 M 6-benzalaminopurine (BAP) or kinetin), which inhibits root growth and promotes tillering, and auxin (10-6 M 2,4-dicilorophenoxyacetic acid (2,4-D) or 10-5 M ?-naphthaleneacetic acid (NAA)), which inhibits the growth of shoot and root. The yield of the seedlings grown from the multiple shoots was very similar to that of seedlings grown from seeds, expect when the multiple shoots were treated with 10-4 M BAP. Treatment of multiple shoots with 10-4 M BAP resulted in a decrease of the harvest index and yield. Seedlings derived from multiple shoots that were maintained for a long period of time showed very similar yield to those from seeds when the multiple shoots were treated with 10-6 M kinetin.