The advent of computer-based prescribing in general practice has made it possible to study a patient's drug use in detail. This study compared the use of inhaled therapy in 100 patients with chronic disease by examining every prescription issued during the year before and the year after initial consultation at a nurse-run asthma clinic. The majority were poorly controlled in that 79% scored high on the Jones Morbidity Index at their first visit. The number of patients on inhaled corticosteroid and salmeterol xinafoate rose from 87 to 100% and 6 to 28%, respectively, while those instructed to take their beta-agonist 'when required' as opposed to a regular dose rose from 26 to 82%. The daily median intake of short-acting beta-agonist fell from 5.0 to 3.8 doses (P < 0.0001). In the 87 patients on inhaled corticosteroid throughout, the mean daily dose increased from 532.1 to 793.1 micrograms (P < 0.0001), and compliance (defined as the total dose issued in 1 year expressed as a percentage of that recommended) increased from 61.5 to 69.3% (P = < 0.05). Attendance at a nurse-run asthma clinic was associated with a number of significant alterations in inhaled therapy. These changes conformed to the British Thoracic Society's guidelines.