The effect of abscisic acid (ABA) and of gibberellic acid (GA2) on the metabolism of kinetin in detached leaves was investigated. Kinetin labelled in either the purine ring or the N-6 substituted side chain was fed into leaves of Rumex pulcher. The leaves were extracted 4 or 20 h later and the extract chromatographed on paper which was subsequently scanned for radioactivity. Four major radioactive peaks were revealed. Two peaks were tentatively identified, one kinetin and its riboside, and the other adenine. ABA effected a significant decrease in the transformation of kinetin to adenine while GA3 had no consistent effect. The possible meaning of this finding is discussed.