This book originated from a series of 14 research studies, which the author undertook over a period of as many years, the purpose of which was to enquire into the underlying principles of computer design in general practice. The book also takes account of other people's published experience in the field of general practice computing and areas related to it - reflected in the Further Reading lists at the end of many of the chapters. Although these lists are not comprehensive they endeavour to represent those contributions in each field which might be considered significant and interesting to general practitioners. The design of currrently marketed systems has stemmed from this earlier corporate research but is now refined in the light of field experience through user groups. This process of refinement has also been noted in the book's content.