Summary Ethylene, dissolved in water, was continuously collected during a 52 h period from three different positions within one ripening apple, Malus domestica (Borkh.) cv. Ribston, using microdialysis. Ethylene was analyzed in the gas phase, at equilibrium with the dialysate, using gas chromatography. The ethylene concentration was about 400 ppm at all three positions and the recovery of ethylene in the dialysis process was around 30 %. The microdialysis probes introduced into the apple were perfused with deionized water at a rate of 2 µL/min. In order to locally inhibit the ethylene production cobaltous ions were introduced by changing the perfusion liquid to 0.5M Co 2+ in one microdialysis probe. As a consequence, the ethylene concentration decreased about 50 % at the treatment site. After a distance dependent time lag ethylene concentration also declined in the other probe positions.