BACKGROUND: We conducted a prospective comparative study to evaluate the potential benefit of computer-assisted prescribing (CAP). We compared the accuracy, completeness and time use of CAP with that of conventional handwritten prescribing at the intensive care unit (ICU) of the John Radcliffe Hospital, Oxford, UK. RESULTS: Twenty-five clinicians and 2409 drug entries were evaluated for accuracy, completeness, legibility and time spent prescribing. One hundred and twenty-eight handwritten and 110 CAP charts were monitored. One hundred percent of CAP charts were complete compared to 47% of handwritten charts.Drug prescriptions were divided into three categories: intravenous fluids, intravenous infusions and intermittent drugs. Percentage of correct entries in each category were 64%, 47.5% and 90% for handwritten, compared to 48%, 32% and 90% for CAP charts, respectively.The mean time taken to prescribe was 20 s for hand written prescribing and 55 s for CAP. CONCLUSIONS: Computer-assisted prescriptions were more complete, signed and dated than handwritten prescriptions. Errors in prescribing, including failure to discontinue a drug were not reduced by CAP. Handwritten prescribing was quicker than CAP. Simple enhancements of the computer software could be introduced which might overcome these deficiencies. CAP was successfully integrated into clinical practice in the ICU.