Sulfadiazine acute nephrotoxicity is reviving specially because of its use in toxoplasmosis in HIV-positive patients. We report 4 cases, one of them in a previously healthy person. Under treatment with sulfadiazine they developed oliguria, abdominal pain, renal failure and showed multiple radiolucent renal calculi in echography. All patients recovered their previous normal renal function after adequate hydration and alcalinization. A nephrostomy tube had to be placed in one of the patients for ureteral lithiasis in a single functional kidney. None of them needed dialysis or a renal biopsy because of a typical benign course. Treatment with sulfadiazine requires exquisite control of renal function, an increase in water ingestion and possibly the alcalinization of the urine. We communicate a case in a previously healthy person, a fact not found in the recent literature. Probably many more cases are not detected. We think that a prospective study would be useful.