Dreams come true? A computerised clinical decision support system (CDSS) is “a computer based tool using explicit knowledge to generate patient specific advice or interpretation”.1 Our use of computers has been driven not only by the increasing need to manage large amounts of information, but also by the imperative to make evidence based and cost effective decisions on a daily basis.2 Furthermore, there is accumulating evidence to prove that computer aided medical tools address the growing information needs of the busy clinician3 and improve healthcare processes as well as patient outcomes.4 In turn, this has led to the rapid proliferation of a variety of CDSS. This leading article summarises the past, present, and future of such systems, with special emphasis on their role in paediatrics. The concept of computerised decision support for medicine is not new. As far back as 1959, a pioneering article in Science described how computers might assist in the process of diagnosis.5 The familiar miniature device used by Dr McCoy to make diagnoses in the Star Trek series evolved out of a similar dream. This section describes some of the various approaches employed to develop previous CDSS. In Warner’s (1961) program for the diagnosis of congenital heart disease, data were drawn from 1035 patients referred for cardiac catheterisation. Given multiple clinical findings, a matrix of 33 different congenital heart diseases and 50 associated clinical findings was used to calculate the probability of a specific diagnosis. The diagnostic accuracy of this system matched that of three congenital heart disease experts.6 This was an early example of a system using Bayes’ probabilistic theory. The eponymous theorem is reported to have been formulated by Reverend Thomas Bayes …