Analysis of the antibodies submitted to the 3 International Workshops on Small Cell Lung Cancer Antigens has resulted in the identification of 15 clusters of antibody reactivity. One of these clusters, named SCLC cluster 2, is characterized by reactivity against an epithelium-associated 38 kDa membrane glycoprotein. SCLC cluster 2, and a number of other antibodies with reportedly similar reactivities, were shown to recognize a protein encoded by the GA733-2 gene, whereas the newly defined SCLC cluster 13 antibodies react with the GA733-1 gene product. We propose to call the antigen detected by SCLC-cluster-2 antibodies "epithelial glycoprotein 2" (EGP-2), and the epithelium-associated glycoprotein recognized by antibodies clustered in SCLC cluster 13 (see elsewhere in this volume) "epithelial glycoprotein 1" (EGP-1). A short overview of the characteristics of both proteins and the applications of anti-EGP-2 antibodies is presented.