Administration of beta-agonist bronchodilators by metered-dose inhaler (MDI) is as effective as administration by hand-held nebulizer (NEB). Recent studies have suggested that MDI therapy is less costly to administer and that routine substitution of MDI for NEB would result in considerable savings to patients and to hospitals. To our knowledge, the actual extent to which MDI therapy would replace NEB therapy or the cost savings realized has not been reported previously. We examined the success and impact on hospital costs of the routine substitution of MDI for NEB therapy in a large tertiary-care hospital. Following introduction of this strategy, more than 60 percent of all aerosol therapy was actually given as MDI. The mean amount of time spent by therapists to provide aerosol therapy was significantly reduced by MDI substitution, falling from 1,576 +/- 131 h/mo, to 992 +/- 116 h/mo (p less than 0.002). The total cost to deliver aerosol therapy fell from $27,600 +/- $2,277/mo to $20,618 +/- $2,086/mo (p = 0.008). Potential cost savings of $83,000 annually were achieved by the hospital, and charges to patients were lowered by approximately $300,000 per year. Routine substitution of MDI therapy for NEB therapy can be accomplished with considerable, but not total, success. This approach results in significant reductions in the cost of health care provision.