We studied the effects of AVG, ACC, and ethylene on the process of adventitious bud formation in vitro from bulb-scale explants of Lilium speciosum Thunb., cv. Rubrum nr. 10. AVG inhibited plantlet regeneration, especially at non-basal sites. The effects of AVG were counteracted by ACC and TIBA. Ethylene, applied in the first 3 or 7 days of the culture period in a concentration of 1 or 10 ppm, caused an increase in bud number per explant and suppressed the predominantly basipetal polarity of the regeneration sites. Ethylene increased the sensitivity of the tissue to exogenous auxin. A model is proposed showing the influence of ethylene, its biosynthetic pathway, and the other modifying factors on the regulation of plantlet induction in bulb-scale explants by auxin.