Clinical trials are important research tools currently used in assessing new drugs and therapeutic strategies, which are unable to produce large effects evaluable in small series of patients. We describe methodological principles of clinical trials and significant advantages in their implementation produced by using a computer network for long-distance modem transmission of echocardiographic images and clinical data. This network has been recently developed in Italy and is operative at the University of Bari and the Associazione per la Ricerca in Cardiologia. Several clinical participating centers of the CEDIM Study and PHASE Study are connected in real time to a data center via modem by a special telephone network (RFD) of the Italian State Telephone Company (SIP). We describe the configuration, main features and applicative potential of such a powerful research tool in modem clinical trial methodology.