The water supply of the three institutions has been continuously disinfected with iodine since October, 1963. The general health and thyroid function of the 29 remaining inmates of the original test group were re-evaluated in December, 1966. All continue to be in good health and have no evidence of impaired thyroid function. Thus, there is no evidence in these subjects that long-term use of an iodinated water supply has been deleterious to health. Additional inmates are being examined and added to the test group. Iodine was added to the water supply of the City of Gainesville, Florida, for a twelve-hour period on February 23, 1967. A dosage of 1 ppm was added to the water which contained about 2 ppm of combined chlorine. Iodine residuals were maintained to the ends of the system by reoxidation of the iodide ion. The year's research concerned with the above is discussed.