In the barly coleptile sections treated with either 1×10^(-5)M abscisic acid (ABA) or 1×10^(-5)M gibberellic acid (GA), the time course changes of ribonuclease (RNase) activity and ribonucleic acid (RNA) profiles were studied. The results may be summarized as follows: 1. While GA suppressed RNase activity, ABA activated it. 2. High level of s-RNA and low level of r-RNA compared with normal plant sections in hormone-untreated coleoptiles seemed to be the results of increased RNase activity in the incubation period. 3. While GA retarded the decomposition of r-RNA, ABA activated it and the results seemed to be related with RNase activity. 4. GA activated the synthesis of RNA-DNA component, and ABA suppressed it. 5. Increase in the amount of s-RNA with the treatment of ABA may be due to the decomposition of r-RNA.