Today many companies show a highly interest in adopting the e-business. However, companies need different information system strategy in the adoption of e-business in order to support information sharing. Information system strategy is concerned with aligning of information system with business needs. Beside this, companies need to search after strategic advantage from information technology, since information system strategy explains what to do with IT. The earlier experiences point to the fact that companies failed to develop their businesses through Internet mainly because they did not developed an appropriate strategy. This study investigates how to implement information system strategy to support information sharing in the context of e-business. Thus, the purpose of this study is to highlight different perspectives in adaptation of information system strategy within e-business companies. The empirical study is based on a qualitative method of data collection by using three interrelated case studies. The study conducted a number of interviews with three e-business companies named Hööks, NetOnNet and Kwintet. The theoretical framework provided knowledge about e-business, information sharing, and information system strategies. The findings - by means of interview questions - were analyzed by theoretical ideas. The authors came to a number of conclusions: 1. Perspectives in information system strategy are divided into different parts consist of ERP system, supporting system, and manual approach, depending on how the ebusiness companies uses the information system strategies. 2. Information system strategies are embedded with ERP system and are interconnectively used companies that use the e-business as their core business system. 3. The e-business provides information workflow to support information sharing. 4. The final conclusion is that there are remaining perspectives, which are not connected to ERP system, but they are vital for the implementation of information system strategies for information sharing.