Pretreatment of cut florets of Laeliocattleya (Lc.) Irene Finney 'York' with 0.1 //I'liter'1 ethylene for 24 hr promoted ACC oxidase activity in petals and ethylene production by florets 3 days after harvest (DAH), and shortened the vase life from 7.5 to 4.0 days. The ethylene treatment did not affect ACC concentration or ACC synthase activity in the petals. Pretreatments with 1- methylcyclopropene (1-MCP) at 0.25, 0.5 and 1 fj, 1 liter"1 for 4 hr significantly prolonged the vase life of Cattleya alliances. In Brassolaeliocattleya Mem. Robert Hack 'Villa Park', ╲JJL 1 · liter'1 1-MCP application suppressed ACC oxidase activity and ethylene production until 2 DAH and doubled their vase life; ethylene production substantially increased after 4 DAH. There was no difference between single and repeated applications of 1-MCP in prolonging vase life in Lc. Sweet Meringue 'Puriavera'. A 5% sucrose vase solution prolonged the vase life of 'Villa Park' and Lc. Irene Finney 'Rachel'. A combined treatment of 1-MCP and BA had synergistic effects on the vase life of 'Villa Park'. A combined treatment of 1-MCP, sucrose and BA was most effective in prolonging vase life. These results indicate that optimum application of 1-MCP with or without sucrose and BA is feasible to prolong vase life of Cattleya alliances.