This study compared the effect of "standard" dose metaproterenol delivered by hand-held nebulizer (HHN) with two puffs of metaproterenol delivered by a metered dose inhaler (MDI) via a spacer (InspirEase) (MDI-spacer). Seventeen patients with an acute exacerbation of obstructive pulmonary disease were studied. Each patient received both MDI-spacer and HHN. Alternate patients were randomized to either MDI-spacer or HHN as initial treatment. Each subject was tested four different times: before and 30 minutes after the initial aerosol delivery technique, and before and 30 minutes after the alternate aerosol delivery technique. Testing consisted of spirometry, lung auscultation, and measurement of vital signs. The interval between treatments for all subjects was 2.96 +/- 0.27 hours (mean +/- SEM) and was not different for subjects who received therapy via MDI-spacer first or HHN first. The patient population studied demonstrated severe airways obstruction (baseline FEV1 33.3 percent predicted +/- 4.9 percent). There was a statistically significant improvement in FVC and FEV1 after metaproterenol delivered by HHN, but not after MDI-spacer. Metaproterenol treatment with HHN resulted in a greater improvement in FEV1 (p less than .05) than MDI-spacer when the data were reported as absolute improvement (0.19 +/- 0.05 L for HHN) vs (0.06 +/- 0.03 L for MDI-spacer) or reported as percent change (23.2 +/- 6.6 percent for HHN) vs (9.5 +/- 3.4 percent for MDI-spacer). Asthmatic patients exhibited a significantly greater (p less than 0.05) improvement in FEV1 after HHN (23.4 +/- 4.7 percent change) than after MDI-spacer (6.6 +/- 4.5 percent change). Patients with chronic obstructive pulmonary disease (COPD) exhibited a greater improvement in FVC (p less than 0.05) after HHN (25.2 +/- 6.7 percent change) than after MDI-spacer (5.8 +/- 4.7 percent change). We conclude that the "standard" dosage of metaproterenol delivered by HHN results in greater spirometric improvement in patients with acute obstructive pulmonary disease than the conventional dosage of metaproterenol delivered by MDI-spacer. It is likely that this reflects the fact that the recommended dose of metaproterenol delivered by MDI is too low and should be increased.