1. Absorption and urinary excretion of 2,4-dichlorophenoxyacetic acid (2,4-D) have been studied in six subjects following oral ingestion (5 mg/kg). 2. 2,4-D is quickly absorbed; significant quantities were detected in plasma 1 h after ingestion. 3. 75% of the administered dose of 2,4-D is excreted unchanged in the urine in 96 h after administration. 4. Lack of metabolic transformation and rapid excretion suggest that cumulative toxicity by 2,4-D is unlikely.