Software industry responded to the need for transactions in the Web service world by publishing several proposals, that are quite alike. These proposals define basically communication protocols that indirectly implement advanced transaction models. However, the rather obvious question "How can I use transactions in Web service orchestrations?" is not covered anywhere satisfyingly. The use of arbitrary advanced transaction models is provided by some of the proposals, but likely requires an update of various transaction system components. This paper introduces TWSO (Transactional Web Service Orchestrations), an approach to integrate transactional processing with Web service orchestrations. It tries to overcome the hassles stated above and provides an XML vocabulary (TWSOL) that is intended to be incorporated in Web service orchestrations. The usage pattern of TWSO is designed to resemble the programming pattern used when nowadays application developers use transaction-enabled components like databases or application servers. Moreover, arbitrary advanced transaction models can be synthesized by using a set of transaction building blocks without the demand for system-updates.