Clinical diagnosis of pathological conditions is accomplished regularly via the recording and subsequent analysis of a physiological variable from a subject. Problems with current common practice centre around the obtrusive and rigid nature of this process. These include the length, timing and location of the diagnostic recording session, transfer of data to clinical staff, liaison between clinical staff and subjects and the integration of such diagnostic check-ups into the overall health care process. We have designed a modular diagnostic monitor that is centered around a wearable computer system which, when integrated into a suitable computer network and database architecture, is capable of addressing the above problems. The system is modular, allowing researchers and practitioners to utilise various sensor modules, reconﬁgure the unit in terms of its on-board storage and wireless telemetry capabilities, select the appropriate level of data preprocessing (before archiving data) and choose the appropriate level and nature of feedback to the subject. The system is GRID enabled, supporting e-clinical-trials. GRID clients can display live data, historical data, or perform data mining.