The objective of this work was to study the responses of two plum (Prunus salicina Lindl.) cultivars ('Golden Japan' and 'Santa Rosa') to ethylene treatments, and to evaluate their postharvest quality. Fruit were harvested at different ripening stages during three consecutive weeks. Exogenous ethylene was applied at 1.0 and 10.0 ppm for 24 hours in closed containers. The results indicated that 'Santa Rosa' plums behaved as a climacteric fruit, since ethylene treatments stimulated the production of auto-catalytic ethylene, and accelerated the changes in colour, soluble solid content and texture, the effects being less notorious at the most advanced ripening stage. On the contrary, 'Golden Japan' plum behaved as a non-climacteric fruit, in which ethylene treatments did not cause any stimulation in the autocatalytic ethylene production or effects in the physic-chemical parameters related to fruit ripening.