This work studies the influence of variations in free polyamines, 1-aminocyclopropane-1-carboxylic acid and ethylene, and their possible relationship, during the different development stages of two carnation cultivars (Dianthus caryophyllus L. cultivars Domingo and Famosa) with noticeable differences in vase life. A pre-treatment with ethylene or silver thiosulphate helped to verify the possible link between polyamines, ethylene biosynthesis and carnation vase life. The senescence periods in carnation petals, both untreated and treated with ethylene (1 ppm for 8 h) and silver thiosulphate (1 mM for 2 h), were studied at 21oC and 60-70% relative humidity during eight different stages of senescence. Famosa (long-life cultivar) was associated with lower ethylene production and 1-aminocyclopropane-1-carboxylic acid concentration in petals compared with Domingo (short vase-life cultivar). The effects of pre-treatments with exogenous ethylene or silver thiosulphate were only evident in the short-life cultivar Domingo, in which ethylene production were increased or reduced, respectively. Silver thiosulphate reduced total ACC content during senescence in Domingo. The total polyamine content in Famosa (128-235 nmol g-1 FW) was lower than in Domingo (220-372 nmol g-1 FW). High free Putrescine and Spermidine concentrations were detected in earlier stages of flower senescence in the short vase-life cultivar. The high percentage of spermine in the petal tissue of 'Famosa' may inhibit ACC accumulation and ethylene production, resulting in increased flower longevity.