The lingual appliance was developed simultaneously in 2 countries during the 1970s. Although not fully recognized by the orthodontic mainstream, lingual treatment has steadily expanded, with increased numbers of lingual orthodontists and patients. This article reviews the development, advantages and disadvantages, bonding techniques, biomechanics, and treatment procedures of the lingual appliance. Currently, there are few contraindications for treatment with the lingual appliance. Cephalometric measurements do not reveal statistically significant differences in treatment results between labial and lingual treatment; however, more clinical trial studies are needed to compare the efficiency and outcome of lingual appliances with those of labial appliances.