The biphasic degradation of delta9-tetrahydrocannabinol (I), as monitored by flame-ionization GLC, produced delta8-tetrahydrocannabinol (II), cannabidiol (X), 9-hydroxyhexahydrocannabinol (VI), 9,10-dihydro-9-hydroxyisocannabidiol (VI), and and 6,12-dihydro-6-hydroxycannabidiol (VIII) in acidic solutions. Further identification was made by GLC, mass spectrometry, and comparison with authentic samples. Only II and IV were produced above pH 4 in the neutral region by first-order kinetics. The acidic degradation of cannabidiol (X) gave I and the products of the acidic degradation of I. The initial phase of acidic I degradation was assigned to the development of solvolytic equilibria among I, VIII, X, and, possibly, isocannabidiol (IX), with the concomitant production of II and IV. Compounds VIII, IX, and X did not appear in the neutral region since ether cleavage occurred only in strong mineral acids. Hydration of the delta9-double bond resulted only in acid-catalyzed equilibria of cleaved ethers with the delta8-configurations and characterized the second phase of acid degradation of I. Cannabinol and hexahydrocannabinol were found together in several cases due to the disproportionation of I as catalyzed by silicic acid, silica gel, and chloroform.