Abstract The uptake, fate and excretion of quinoline yellow in the rat were studied. In the isolated perfused liver 70% of the dose was excreted into the bile within 3 hr. Similar results were obtained after intravenous injection into anaesthetized animals. When given by gavage, only about 1% was excreted in bile and urine within 4–5 hr. Quinoline yellow administered orally to rats was quantitatively excreted, the excretion being mainly faecal. Administration of quinoline yellow did not affect the activities of two microsomal enzymes, N-aminopyrine demethylase and aniline hydroxylase. It is concluded that very little quinoline yellow is absorbed from the gastro-intestinal tract of the rat. No evidence of metabolism was obtained.