Ten Egyptian Water buffaloes in mid-lactation were stratified by weight and milk production and randomly assigned into two treatment groups; a control group (A) receiving no iodine (12) supplement and an 1, -treated group (B) receiving sup < /strong>plemental dietary 1, two times weekly on the basis of 0.2 mg 1g/kg body weight p < /strong>er day. All animals were fed a concentrate and roughage (60:40 DM basis) diet to cover their requirements for maintenance and p < /strong>roduction, during a 2 wk p < /strong>reliminary and 7 wk exp < /strong>erimental periods. Milk and blood samples were obtained at wk 3, 5 and 7 of the experimental period and analyzed for certain constituents. At wk 7 of the experimental period, 1,-treated animals (B) had 40% more (P<.02) serum tri-iodothyronine (Tz) and 67% more (P<.05) triglycerides and 20% less (P<.10) cholesterol concentrations than controls (A). Serum total proteins and globulins levels were 8.5% and 12% lower (P<.10) in B group compared with A group < /strong>, respectively. Serum glucose and urea nitrogen concentrations tended to be slightly higher, whereas albumin tended to be slightly lower in B group compared with A. Serum total bilirubin at wk 3 was 32% lower (P<.05) in B group compared with A and did not differ significantly (P>.10) at wk 5 and 7. Means of milk yield, fat% and 7% fat-corrected milk slightly increased and at wk 5 total solids% significantly increased due to 12 treatment. No deleterious effects on animal health attributable to treatment were observed. (Key Words: Iodine, Thyroid hormone, blood, milk, buffaloes).