1. The excretion of water has been studied in a large number of experiments on rabbits. After the ingestion of 100 cc. of water, the day before the experiment and as part of the experiment, the average diuresis amounted to 0.6 cc. per minute during a half hour period. The highest individual rate was 1.5 cc. per minute.
2. The excretion of cyanol and of azofuchsin I has also been studied. It has been shown that the cyanol excretion curve closely parallels the inulin excretion curve of Kaplan and Smith. Evidence is presented that cyanol is disposed of entirely or mainly by filtration.
3. The excretion of azofuchsin I is not only very different from that of cyanol or inulin, but almost identical with that of phenol red. Evidence is presented that at low plasma concentration azofuchsin is, in the main, secreted.