The disposition of sulfatroxazole (STZ) has been studied in goats and pigs after intravenous administration of a single dose. The percentage of protein‐binding decreased with increasing plasma concentration in both species. At 100 μg/ml about 85% was bound to plasma proteins in goats, while the corresponding value was only 55% in pigs. Two metabolites of STZ were isolated from urine and identified as N4‐acetyl‐STZ and 3‐sulfaniIarnido‐4‐methyl‐5‐hydroxy‐methyl‐isoxazole (5′‐OH‐STZ). The goats excreted about 80% of the dose in urine. The majority (64%) was excreted as unchanged STZ, while N4‐acetyl‐STZ and 5′‐OH‐STZ made up 19% and 18%, respectively. The pigs excreted 95% of the dose in urine. Unchanged STZ amounted to 30% and N4‐acetyl‐STZ to 70% of the urinary excretion in pigs, w