The increasing recognition of the participation of free radical-mediated oxidative events in the initiation and/or progression of cardiovascular, tumoural, inflammatory and neurodegenerative disorders, has given rise to the search for new antioxidant molecules. An important source of such molecules has been plants for which there is an ethno-cultural base for health promotion. An important example of this is boldo (Peumus boldus Mol.), a chilean tree whose leaves have been traditionally employed in folk medicine and is now widely recognized as a herbal remedy by a number of pharmacopoeias. Boldo leaves are rich in several aporphine-like alkaloids, of which boldine is the most abundant one. Research conducted during the early 1990s led to the discovery that boldine is one of the most potent natural antioxidants. Prompted by the latter, a large and increasing number of studies emerged, which have focused on characterizing some of the pharmacological properties that may arise from the free radical-scavenging properties of boldine. The present review attempts to exhaustively cover and discuss such studies, placing particular attention on research conducted during the last decade. Mechanistic aspects and structure-activity data are discussed. The review encompasses pharmacological actions, which arise from its antioxidant properties (e.g., cyto-protective, anti-tumour promoting, anti-inflammatory, anti-diabetic and anti-atherogenic actions), as well as those that do not seem to be associated with such activity (e.g., vasorelaxing, anti-trypanocidal, immuno- and neuro-modulator, cholagogic and/or choleretic actions). Based on the pharmacological and toxicological data now available, further research needs and recommendations are suggested to define the actual potential of boldine for its use in humans.