The quality of 1,315 interventions made by pharmacists over a 12‐month period at Harefield hospital, a 180‐bed cardiothoracic hospital, was measured using a six‐point scoring system. The system was validated by comparing a pharmacist's scores with doctors' scores on a sample of the interventions. Using the scoring system, 53 per cent of the interventions could be said to lead to an improvement in patient care, but only 2 per cent prevented major adverse reactions. No potentially life‐saving interventions or any which were detrimental to patients' care were recorded. It is concluded that pharmacists do have a role in improving the quality of patie