Abstract: A clinical trial data capture system has clinical site computers (6), each registered with a site and having thick client software, and a server (2) programmed to receive clinical data from the site computers and to analyse said data in real time. The server (2) automatically determines if a site computer is outside of an allowed region, indicating unauthorised use, and takes an action such as clearing the computer's data. Each site computer performs cycle management by maintaining a workflow (14) per patient, and imposes a consent gate through to subsequent workflow stages of patient treatment with n visits V1 . . . Vi . . . Vn, and treatment follow-up. A distribution lplot is generated (27) for parameters when data is close to thresholds and a threshold may be automatically modified accordingly.