The bronchodilating activity of oral cannabinoids was evaluated in three double‐blind experiments that involved the study of dose‐response and interactive relationships and the potential development of tolerance. Data indicated that ▵8‐tetrahydrocannabinol (▵8‐THC), cannabinol (CBN), and cannabidiol (CBD) in maximal doses of 75 mg, 1200 mg, and 1200 mg, respectively, did not induce significant dose‐related physiologic effects in experienced marijuana smokers. ▵8‐THC (75 mg) was, however, associated with bronchodilation, tachycardia, and peak highs less than that after ▵9‐tetrahydrocannabinol (▵9‐THC). The combinations of CBN and CBD with low‐dose ▵9‐THC (5 mg) did not induce significant bronchodilation but did exert interactive effects on heart rate and “high.” A 20‐day study of daily ▵9‐THC (20 mg), CBN (600 mg), and CBD (1200 mg) did not indicate tolerance or reverse tolerance to any drug. We conclude that ▵9‐THC and, to a lesser extent, ▵8‐THC, have acute bronchodilator activity but that CBN, CBD, and their combinations do not provide effective bronchodilation. The daily use of ▵9‐THC was not associated with clinical tolerance.Clinical Pharmacology a