The bronchodilator effects of cumulative doses of terbutaline 0.125 mg, 0.125 mg and 0.250 mg administered as a pressurized aerosol via a pear shaped spacer were compared with those of terbutaline 1.25 mg, 1.25 mg and 2.50 mg administered as a nebulized solution via a PARI-inhaler Boy. FEV1.0 and flow-volume curves in 13 patients were measured. Initial placebo treatment of both groups resulted in a significant increase in FEV1.0, especially when it was given in nebulized form. The increase after active drug was significant after 15 min, with only minor changes during the rest of the trial. The log-dose/increase in FEV1.0 showed that equipotent doses of pressurized and nebulized terbutaline were in the ratio 1 to 4. Administration by nebulization offered no clear advantage over use of a pressurized aerosol with a pearshaped spacer.