AbstractThe objective of this research was to develop a rapid morphological test for proliferating cells using diaminobenzidine as the substrate marker. This technique can be employed to visualize proliferating cells by using a monoclonal antibody to bromodeoxyuridine and a standard immunoperoxidase technique. This paper describes methods for the rapid demonstration of S-phase nuclei in routine paraffin tissue sections. The tissue was fixed by exposure to microwave irradiation for various times and temperatures. The subsequent staining results are reliable and can easily fit into an existing immunoperoxidase program. (The J Histotechnol12:101, 1989.)