1. Needle acupuncture was performed at three sites in twenty patients in a clinical attack of bronchial asthma. 2. In all patients the symptoms of bronchoconstriction improved during the attacks when the correct site was stimulated, and in five patients wheezing was abolished. 3. Stimulation at the correct site produced a significant increase in the mean FEV1-0 (58%) and FVC (29%) but not in maximal mid-expiratory flow rate (MMFR; 76%), when compared with the findings before acupuncture, along with a significant fall in the Pa,CO2 and an insignificant fall in Pa,O2. A mild tachycardia was also observed. 4. After acupuncture a greater improvement in FEV1-0, FVC and MMFR was produced by inhalation of isoprenaline. 5. No significant changes in FEV1-0, FVC, MMFR, pulse rate or arterial blood gas tensions occurred after acupuncture at control sites. 6. In four of the patients during clinical remission acupuncture was performed before and after histamine aerosol challenge, but there was no effect on either the severity or the duration of the histamine-induced bronchoconstriction. 7. It is concluded that acupunture probably reduced the reflex component of the bronchoconstriction, but failed to influence direct smooth muscle constriction caused by histamine.