Application of 1000 ppm ethylene for 24 h did not induce earlier onset of ethylene production when applied on harvest day, but was effective when applied one day or five days after harvest. The results indicate that purple passion fruit produces ethylene with the same biosynthetic pathway as other tissues in higher plants; its ethylene biosynthesis is regulated mainly by ACC synthase activity, and the sensitivity to ethylene might have changed after harvest as the fruit ripened.