: Electronic B2B marketplaces bring together many online suppliers and buyers, each of which can potentially use his own format to represent the products in his product catalog. The marketplaces have to perform non-trivial mappings of these catalogs. In this paper we analyze the problems which occur during integration, taking several leading XML and non-XML formats as examples. We discuss the method for applying XSLT technology to the integration problems, propose typical solutions to these problems, and give the corresponding examples of integration rules.