This will be a randomized prospective dose escalation clinical study of N-acetylcysteine (NAC) in patients with stage 3 or worse renal failure (Glomerular Filtration Rate 30-60 ml/min calculated with the Modification of Diet in Renal Disease formula), undergoing a procedure or imaging that requires the administration of contrast media at Oregon Health & Science University or the Portland Veterans Hospital. Subjects will receive NAC 60 minutes prior to the procedure or imaging requiring contrast media. Toxicity will be graded according to NCI Common Toxicity Criteria (CTC) version 3.0. An adult Phase 1 dose escalation study of NAC administered intravenously (IV) and intra-arterially (IA) will be performed. An isotonic nonionic contrast agent will be used in all cases. Contrast Induced Nephropathy (CIN) is defined as an increase in serum creatinine concentration of 25% or more from the subjects baseline value within a 72-hour period after the administration of contrast media. Serum creatinine concentration will be measured at admission, every day during in-patient hospitalization, and at hospital discharge.