Metabolic changes in developing rice seeds were studied with respect to respiration, carbohydrate and nitrogen fractions, nucleic acids and hydrolytic enzymes, viz. α‐amylase, adenosine triphosphatase (ATPase) and phytase. — Respiration rate was maximum after 12 days from the date of pollination and became feeble afterwards with the fall in the moisture content of the maturing seeds. In the early stage, there was a preponderance of reducing sugars which were replaced later by nonreducing forms. Dry matter accumulation was mainly due to the steady rise in starch content. There was a gradual accumulation of protein nitrogen throughout the experiment, the rate being highest between 12–16 days. RNA content increased steadily till the seeds became mature, while DNA formed rapidly during the first 20 days and was maintained at the same level thereafter. —α‐Amylase activity increased up to 20 days and declined sharply afterwards. The peak activities of ATPase and phytase were recorded at 32 and 24 days after pollination, respectively. Copyright © 1971, Wiley Blackwell. All rights reserved