The aim of this study was to compare the immediate and long-term bronchodilator effect as well as the patient acceptability of a 2-week, multidrug, inhalation treatment delivered by a metered dose inhaler (MDI) versus a jet nebulizer in a group of elderly patients with chronic obstructive pulmonary disease (COPD) or asthma and an at least partially reversible airflow obstruction. Twenty elderly outpatients (17 men; mean +/- SD age, 67 +/- 2 years; mean +/- SD baseline forced expiratory volume in 1 second [FEV1], 46.5 +/- 14% of predicted value) with COPD or asthma participated in the study, which was of an open, randomized, crossover design. After a 1-day baseline evaluation, including patient history, clinical examination, and spirometry, participants were randomly assigned to receive a multidrug inhalation treatment (a combination of salbutamol, ipratropium, and flunisolide) with either an MDI or a jet nebulizer. Two weeks later, they were shifted to treatment with the alternative system for a further 2 weeks. FEV1 was measured on the first and fourteenth days of each treatment period, on each occasion both before and 30 minutes after the morning inhalation. At the end of the study, patients were asked to express a personal preference for one of the two inhalation treatments with regard to effectiveness and acceptability by filling out a simple questionnaire. Both the MDI and jet nebulizer had a significant immediate bronchodilator effect on the first and fourteenth days of treatment, with no differences between treatments. No long-term bronchodilator effect was seen with either aerosol delivery system. Patient preferences were clearly in favor of the jet nebulizer with regard to effectiveness and in favor of the MDI with regard to acceptability. In conclusion, in elderly patients with COPD or asthma and partially reversible airflow obstruction, a maintenance multidrug bronchodilator/anti-inflammatory inhalation treatment produced a statistically significant and clinically relevant bronchodilator effect without substantial differences between the two delivery systems. Most patients considered the MDI to be more acceptable and the jet nebulizer to be more effective. These preferences should be taken into consideration when prescribing a maintenance aerosol inhalation treatment.