The costs and effects on patient management following the introduction of a fully automated blood count analyser have been evaluated for a hospital haematology laboratory in England, during 1985. In the case of the relatively high throughput observed in the laboratory studied, the automated technology was judged to be cheaper if considering laboratory-centred costs alone. But this was no longer necessarily the case once wider costs, including extra medical workload generated for hospital and community physicians, were included. Effects on patient management were measured for all types of patient, including hospital in-patients, out-patients and general practice patients. A graphical method allowing comparison of the costs and effects of the replacement automated system, termed a Technology MAP (Management Awareness Profile) is presented in the paper. MAPs provide a flexible information display which can be tailored to an individual laboratory's situation producing an overall picture of expected costs and effects on patient management following the introduction of a new technology--a full value-in-use assessment. The authors argue that there is a need for a central source of such value-in-use assessments, especially for new medium-priced diagnostic technologies which are likely to become widely spread in Britain.