Bronchodilator aerosols, if used correctly, have many advantages over other therapies in patients with chronic airflow limitation caused by asthma or chronic bronchitis. The use of pressurized aerosol inhalers was examined in a district general hospital: of 57 patients on these inhalers, 39 were unable to use the inhaler effectively, and 23 had never received any advice on inhaler technique. A single demonstration of correct technique decreased the failures to 21 patients and, after two demonstrations, to ten. The cost of the misused inhalers in this relatively small population was 450 pounds, and obviously this figure escalates when the prescription for these inhalers is repeated monthly. It is also increased when the total numbers of misused inhalers in the country are accounted for. The cost in terms of finance, in these days of medical audit and drug budgets, and, more importantly, in terms of patient health, is unacceptable and can be avoided by repeated tuition of technique.