Ethephon, one of the chemicals releasing ethylene, induced flower bud blasting of a Cymbidium hybrid (C. ×Sazanami 'Haru-no-umi') regardless of the stage of flower buds. Both silver-thiosulphate (STS) and gibberellic acid (GA₃) overcame the inhibition of flower bud development induced by high temperatures. There was, however, a distinct difference in the action between these chemicals. The stimulation of flower bud development by STS remained after subsequent applications of ethephon; that of GA₃ was nullified by ethephon. Furthermore, inflorescences treated with STS evolved more ethylene than did the control, whereas inflorescences treated with GA₃ evolved less ethylene than did the control. These results indicate that STS and GA₃ function as inhibitors of ethylene action and ethylene synthesis, respectively. They also indicate that ethylene is involved in high temperature-induced blasting of Cymbidium flower buds.