Large numbers of normal chrysanthemum plants were produced from tissue cultures derived from 0.5 mm high shoot-tips. The cultures, which consisted of callus with superficial meristems, doubled in weight every 3 days in liquid Murashige-Skoog medium containing 2.0 mg/1 kinetin and 0.02 mg/1 NAA. Cultures resumed growth after at least 6 months storage at 4.5°C. Plantlets formed within 6-12 weeks when small pieces of tissue were transferred to agar media containing 0.5-2.0 mg/1 kinetin. Addition of GA3 (10 mg/1) promoted formation and elongation of leaves and shoots on the tissue. Ability to form plantlets was retained after repeated subculture; a culture started in April 1970 is still producing plantlets. One thousand plantlets were potted and grown in the greenhouse. Small (<1 cm high) plantlets initially grew more slowly than larger ones but almost all plants produced normal white flowers after 2 months short day treatment. This system could produce up to 9 × 1014 plantlets or 90 billion 15 cm plants within a year, a great increase over the number possible via conventional propagation.