The EUROMED-ETS pilot system offers a number of security functionalities using off-the-shelf available products, in order to protect Web-based medical applications. The basic concept used by the proposed security architecture is the Trusted Third Party (TTP). A TTP is used in order to generate, distribute and revoke digital certificates to medical practitioners and healthcare organizations that wish to communicate securely. Digital certificates and digital signatures are used to provide peer and data origin authentication and access control. The paper demonstrates how TTPs can be used effectively in order to develop medical applications that run securely over the World Wide Web.