Immunohistochemistry is a valuable molecular technique based upon the principle of antibody specificity for target antigens in tissues with subsequent development of an amplified colorimetric signal. When staining specificity is ensured with the use of an isotype control, it allows for semiquantitative comparisons, tissue/cellular localization, and inference regarding activation status of proteins of interest. Here we describe a protocol for immunohistochemical analysis of NF-κB family members in fresh frozen human tumor samples.