Few studies have attempted to measure the effectiveness of computerised test-order entry systems to reduce test turnaround time and the extent to which improvements are sustained or continue over time. Further, a recent study has raised the possibility that such systems, which require significant work practice change, may be associated with an increase in mortality rates. Our study answered two questions in relation to the introduction of a computerised pathology order entry system in a major Australian teaching hospital: i) are initial improvements in turnaround times achieved in the first 12 months of system use sustained beyond this time; and ii) did mortality rates change following the introduction of the order entry system? We found significant improvements in turnaround times 12 and 24 months following system implementation and no change in average number of tests per patient. The mortality rate significantly increased in the year following system introduction but returned to the pre-system rate in the second year of system use. Review of the excess deaths demonstrated that these were most likely attributable to a coincidental influenza outbreak and not to system introduction. The computerised order entry systems produced sustained and continuing improvements in health care delivery efficiency over a two year period. Associations between increased mortality rates and system introduction should be investigated carefully to ascertain any likely association.