 In patients undergoing coronary angiography, the incidence of contrast induced nephropathyCINvaries widely and ranges from 5 in the lowest risk patients, to nearly 50 in the highest risk patients. Prior data has shown oral n-acetyl cysteine NAC to be effective in reducing the incidence of CIN.Due to extensive first pass metabolism, the bioavailability of oral NAC is poor and ranges from 4-10. We hypothesize that the incidence of CIN will be reduced in patients with ACS who undergo PCI by the prophylactic administration of intravenous NAC. 