The structural elucidation of five components isolated from Parabaena sagittata is described. The plant is a climber indigenous to northern Thailand and has been used by the hill tribes for medicinal purposes. Three of the components are known natural products: the cyclohexanepentol, (+)-protoquercitol (1); the tetrahydroprotoberberine, (-)-tetrahydropalmatine (4); and the protoberberine, berberine. The other two components are previously unreported tetrahydroprotoberberines and have been given the names (-)-O-methylthaicanine (2) and (-)-thaicanine (3). Their structures were assigned after detailed analysis of their 'H- and '3C-nmr spectra. Methylation of 3 was shown to yield 2; 2 and 3 are the first reported examples of protoberberines with substituents at the 4-position.