Local anaesthetics are frequently administered preceding oral treatment. Since little is known about the incidence of adverse effects after administration of local anaesthetics, a prospective study involving a group of 219 patients was performed. The most frequently observed complications were insufficient anaesthesia (17%) and positive blood aspiration (3%). Pain during administration, paralysis, blanching, haematoma, and vasovagal collapse occurred each in less than 1% of the patients. The results suggested that administration of local anaesthetics involves a limited risk of adverse events and that the adverse events are usually minor and transient.