Three candidate chemical ripeners showing exceptional activity in screening tests with plantlets were reevaluated in young-adult cane, 14 weeks of age, having fully-developed canopies and millable stems. Polaris, and CP 70139 (Monsanto Agricultural Products Co.) and PP 757 (ICI United States, Inc.) were readministered to the same variety identically propagated by sand culture. Two previously inactive materials, RH 1622 (Rohm and Haas Co.) and Ripenthol (Pennwalt Corp.), were also reexamined. Treatment interval was extended from 21 to 42 days. Polaris, CP 70139, and PP 757 again excelled in their effects on growth, tissue sugar and protein components, and enzyme behavior, while RH 1622 and Ripenthol produced little response. Juice quality was significantly improved by the three compounds. Early-adult responses closely conformed to those obtained with plantlets. Results are discussed in terms of an increased validity for ripener screening with plantlets. The young-adult cane is further discussed as a model for efficiency studies on successful candidate materials.