The aim of this cross-sectional study was to investigate the prevalence and several risk indicators of root cariës in 45 periodontal maintenance patients, who had been actively treated for adult periodontitis 11-22 years ago. These patients were part of a routine 3-6 monthly maintenance schedule. Active and inactive root caries and root fillings were recorded, as well as coronal caries experience. Plaque and bleeding scores, number of exposed root surfaces, rate of saliva secretion, saliva buffercapacity, S.mutans counts and Lactobacilli were also scored. From the total of 45 subjects, 37 patients (82%) showed root lesions (root caries and/or fillings), while only 8 patients were free of any root lesions. On average, there were 4.3 lesions per patient (range 0-19) in the present study. Of all damaged root surfaces, 9% were active lesions, mostly located on mandibular teeth at lingual and vestibular sites; 40% were inactive lesions often detected at vestibular sites. The remaining damaged root surfaces (51%) were restored; they were equally divided over both jaws. A higher number of root lesions was observed in those patients with > 106 S.mutans/ml saliva. Although the actual number of lesions per patient was low in relation to the large number of sites with gingival recession, the results from this cross-sectional study in periodontal maintenance patients indicate that: root cariës can be regarded as a complication in periodontal maintenance patients, that the individual number of root lesions correlate with individual dental plaque score, that a high number of root lesions is associated with counts of salivary S.mutans, and that no relation between root cariës and coronal caries experience, salivary secretion rate or salivary buffering capacity seems present. Therefore, repeated oral hygiëne instructions and adjunctive preventive measures including diet counseling and fluoride rinses, as well as fluoride and chlorhexidine varnishes, should be advocated in high-risk patients.