Theophylline-7-acetic acid (T7AA) was administered intravenously to rabbits so that its distribution and rate of elimination could be ascertained. The analytical techniques used were liquid scintillation counting (14C) and high pressure liquid chromatography. T7AA was eliminated rapidly in the urine; the T 1/2 was 11.6 min. This drug appears to accumulate in the kidney because after 60 min, approximately 15 per cent of the intravenous dose was found in that organ.