Flowers of cvs. Winter Nelis and Bartlett contained an equivalent amount of an acidic, auxin-like substance, which decreased in the following 30 days. Thereafter, until 70 days after full bloom (AFB), the substance increased in parthenocarpic ‘Bartlett’, remained relatively constant in seeded ‘Bartlett’, and declined in ‘Winter Nelis’. A neutral auxin-like promoter was detectable in flowers of the 2 cultivars, reaching a maximum between 40 and 65 days AFB. Also, flowers and fruitlets of both cultivars contained extractable gibberellin-like substances which were in greatest abundance about 25 days AFB. The concn of these GA-like promoters at this time was greater in parthenocarpic ‘Bartlett’ fruits than in seeded fruits of either cultivar. Relatively large amounts of an abscisic acid-like (ABA-like) inhibitor were present in ‘Bartlett’ and ‘Winter Nelis’ fruits for a short time AFB. The concn subsequently decreased in both cultivars, but in ‘Winter Nelis’ it increased again toward maturity. Pear extracts contained a bound inhibitor which was active after hydrolysis with β-glucosidase. Seeds of both cultivars and unfertilized ovules of parthenocarpic ‘Bartlett’ fruits had similar levels of an ABA-like inhibitor which increased concurrently with fruit growth. Inhibitors are present throughout fruit development, in contrast to promoters, which occur in sequential order.