e-Business and Enterprise Information Systems have held the spotlight since Internet and World-Wide-Web came out to the world. The e-Business applications have been evolved from legacy client-server architecture into n-tier architecture, lately even into Enterprise Information Systems. There are two famous approaches to build the e-Business applications, which are J2EE and .NET. In this paper, e-Business and n-tier architecture are illustrated. Besides, n-tier architecture for Enterprise Information Systems is introduced, which provide the access to the disparate data sources. In addition, J2EE and .NET are compared for e-Business applications based on many criteria including the methodologies to implement Enterprise Information Systems.