Over a dozen studies have been conducted on the prevalence of and factors associated with root caries, yet our knowledge of this disease process remains limited. This is due, in large part, to a lack of consistency of reporting among the studies undertaken and the wide spectrum of population groups investigated. Nevertheless, the occurrence of root caries is between 20 and 40 percent in healthy, urban adults. Certain population groups such as the institutionalized elderly and patients with periodontal disease tend to exhibit much larger prevalence rates. New root caries develops slowly and tends to be concentrated in a few individuals, usually on the buccal and proximal surfaces of teeth. It is generally accepted that only roots with gingival recession are susceptible to root caries and that age, sex, oral hygiene, diet, saliva, systemic fluoride and previous carious experience have been shown to be associated factors. The next wave of investigations of root canes should focus on testing hypotheses relating to causation so that efficacious preventive and treatment procedures can be developed.