The computer system developed at St Mary's Hospital Medical School, and now used in six hospital haematology laboratories, is described. The system allows for the rapid retrieval of pathology results from an archive of at least 180 000 records on a 10 megabyte disk. Two main data files are used, the "Current File", from which reports are prepared, and an "Archive File" which contains cumulated results. The files are indexed by parts of both the name and, if available, the hospital number. Patient linkage is accomplished using the whole known identification, but, unlike most other systems, no absolute requirement is placed on the existence of a hospital number. It is concluded that this method of patient linkage removes many of the management overheads associated with hospital number linked systems, and that use of the computer not only aids reporting, but also improves quality control and provides data for research.