An open multicenter trial was performed in 242 subjects with chronic obstructive airways disease between August 1987 and April 1989. Two hundred thirty-six subjects were evaluated with regard to safety (m 137, f 99, mean age 49.4 (18-77) years) and 204 subjects with regard to therapeutic efficacy (m 120, f 84, mean age 49.2 (18-77) years). Twelve micrograms (one puff) formoterol was given by metered-dose inhaler twice daily. Investigations were performed at days 0, 14, and subsequently in monthly intervals. Twenty-one patients (10.3%) were sufficiently treated by formoterol alone. One hundred and eighty-three (89.7%) required additional medication, which could be reduced in 90 cases (45.6%). Initially symptoms were present in 201 of 204 patients. At 1 year, 43 patients (21.1%) were symptom-free. At day 0 32.4% of the patients felt "very good" or "good." At 1 year the rate increased to 68.1%. Raw decreased from 0.52 +/- 0.26 (0.06-2.11) kPa.L-1.S at day 0 to 0.33 +/- 0.14 (0.06-0.88) kPa.L-1.S (= -43.5%) at 1 year. FEV1 increased from 1.90 +/- 0.80 to 2.54 +/- 0.97 L (33.7%). The global assessment of therapeutic efficacy was classified as "very good" in 51% (patients) and 47% (doctors), respectively, and as "good" in 38.7% and 42.0%, respectively. Tolerability was "very good" in 82.3% (patients, doctors), and "good" in 12.7% (patients) or 13.7% (doctors). The treatment did not influence blood pressure or heart rate. Twenty-nine patients (12.3% of 236) reported unwanted 39 side effects, such as tremor (6.36%), headache (2.54%), dryness of the mouth (1.27%), cough (0.85%), and dizziness (0.85%).(ABSTRACT TRUNCATED AT 250 WORDS)