Radioactive acetate was fed to Rumex obtusifolius plants and after 7 days aloe-emodin, chrysophanol and emodin were isolated and found to be radioactive. Each was degraded to phthalic acids and the proportion of radioactivity present in the acids shown to be consistent with the acetate-malonate route earlier established for a related species of Rumex. The subsequent fate of the anthraquinones was studied by observing the changes in glycosidic and free anthraquinones in developing fruits and by feeding radioactive aglycones to the inflorescences. The results indicate a rapid utilization of the anthraquinones in the early stages of fruit formation, followed by a more gradual use, and coincide well with similar work on the developing fruits of Cassia acutifolia.