Oxidative stress is increasingly suspected to contribute to the initiation and progression of many disease, including those caused by alcohol exposure. Two major products of reactive oxygen and nitrogen species formation are 4OH-nonenal and 3-nitrotyrosine protein adducts, both of which can be detected by immunohistochemistry. In the past, immunohistochemical techniques have served largely as qualitative measures of changes. However, coupled with digital capture and analysis of photomicrographs, one can now quantitate treatment-related changes with immunohistochemistry. This chapter summarizes techniques for immunohistochemical detection of these products of reactive oxygen and nitrogen species and subsequent image-analysis. Although the methods described herein are based on liver, these techniques have been employed successfully in most tissue types with minor modifications and are therefore broadly applicable.