The most critical factor for interpreting the results of immunohistochemistry is verification of antibody sensitivity and specificity. While some manufacturers supply material data sheets with this information, many do not. This paper describes a well-defined quality assurance program for testing immune reagents. This program can be used to provide commercial suppliers of antisera with analyses of their products destined for government licensure applications. This paper illustrates the protocol and explains the testing philosophy developed over the last eight years.