A statement about metformin and radiographic contrast material in the article “Evaluation of Asymptomatic Microscopic Hematuria in Adults” (September 15, 1999, page 1143) requires clarification. Starting with the third sentence of the third complete paragraph on page 1148, the paragraph should have read as follows: “Because of potential exacerbation of acute renal failure and lactic acidosis, metformin should be discontinued at the time of radiologic studies involving intravascular administration of iodinated contrast materials and withheld for 48 hours subsequent to the procedure. It should be reinstituted only after renal function has been reevaluated and found to be normal.” The statement in the article reflected current recommendations at the time the article was written. However, a new recommendation had been issued by January 1999, according to Bristol-Myers Squibb.