Following a single i. v. injection of sulphadiazine, sulphadimidine and sulphathiazole in buffaloes (100 mg./kg. b. wt.), it was found that: 1. Sulphathiazole was the most rapidly eliminated, with a half-life value of 198 min, followed by sulphadiazine (230 min); sulphadimidine had the slowest rate (563 min). The volumes of distribution of the 3 sulphonamides were 579, 751 and 452 ml./kg. b. wt., respectively. 2. 24 h after injection no detectable amount of sulphadiazine, but a significant amount of sulphathiazole (10.10 μg./ml.) and sulphadimidine (40.54 μg./ml.), was found in plasma. The protein-bindung tendency of the 3 sulphonamides, as calculated in vitro, showed that values for sulphadiazine and sulphathiazole were very similar (18.01 and 16.62 %, respectively), while that for sulphadimidine (4.31 %), was much lower. 3. Excretion of the 3 sulphonamides in saliva was higher than in milk, with the concentration of sulphadimidine in both higher than that of the other 2 compounds. Very high concentrations of the parent sulphonamides and their acetylated derivatives were found in urine.