Genetic improvement of flower vase life is an important breeding target. A breeding program aimed to improve the vase life of carnations (Dianthus caryophyllus L.) that carried out by repeatedly crossing and selecting promising progenies was effective. Thus, we developed many carnation lines with extremely long vase life by using the conventional cross-breeding technique. Selected lines from second-, third- and fourth-generation have vase lives that are 2.7 to 4.1 times longer than the control cultivar, ‘White Sim’. The mean vase life of line 108-44 was 23.6 days in 2003 and 19.1 days in 2004 (414% and 341% of ‘White Sim’ flower longevity, respectively). All selected lines showed low ethylene production in whole flowers during senescence. In addition, the petals and the gynoecia of three selected lines 908-46, 702-21, and 006-13, produced only trace amounts of ethylene during senescence, indicating that the ethylene biosynthesis pathway in these lines was almost completely blocked during senescence. Although ethylene sensitivity of the selected lines was generally high on day 0, immediately after harvesting, ethylene sensitivity after anthesis rapidly decreased with age in the three selected lines. These lines became completely ethylene-insensitive or showed low sensitivity at the end of senescence. Autocatalytic ethylene production by the gynoecia and petals of the three selected lines also decreased on days 3 and 6, respectively, after harvest.