`Bartlett' pears (Pyrus communis L.) were harvested at commercial maturity (average flesh firmness of 18 lb), stored at 30F for 0, 2, or 4 weeks, and then placed into a ripening room at 68F with or without ethylene to evaluate ripening activities. Pears that were stored in air at 30F for <4 weeks did not ripen after 7 days at 68F in an ethylene-free (no-ethylene) room. These pears ripened normally and uniformly after 7 days at 68F in a room enriched with 100 ppm ethylene (yes-ethylene). `Bartlett' pears that were stored in air at 30F for 4 weeks ripened normally after 5 days at 68F in the yes-ethylene room or 6 days at 68F in the no-ethylene room. The amount of cans produced per ton of fresh processed pears can be maximized most economically by exposing freshly harvested `Bartlett' pears to 100 ppm ethylene at 68F for 7 days before canning.

D 'Anjou 'pears (Pyrus communis, L.) harvested at an optimum maturity with the Jeshjrmness (FF) of 66.7N required 8 weeks of chilling at-IC in order to initiate normal ripening in an ethylene-free environment at room temperature. If harvestedfiuit were not exposed to chilling or chilled at-1 C for less than 8 weeks, they could be preconditioned with I00 ppm ethylene for 3 days at 20C to initiate normal ripening. Fruit preconditioned with ethylene were capable of softening normally, reducing extractable juice, decreasing titratable acidity, and showing the climacteric rise of ethylene production during ripening at 20C when treatedfiuit had been further held at -1C in air for 14 days. The properly ripened fiuit developed an acceptable dessert quality. When 'd 'Anjou ' fiuits had been stored at -I C in air for 8 weeks or longer, they could also be preconditioned without ethylene for 3 days at 20C to enhance ripening capacity. The nonethylene preconditioned fiuit were capable of ripening normally following 14 days in simulated transit at -IC and upon arrival in retail markets at room temperature.