The prevalence of caries and caries risk factors was studied among 120 consecutively hospitalized elderly persons. Coronal caries was recorded using the WHO criteria, and active and inactive root caries in accordance with Fejerskov et al. The CPITN was used to evaluate the periodontal state and plaque accumulation in accordance with Löe&Silness. Of the 1212 teeth examined 5% had active coronal caries (2% inactive), 14% active root caries (2% inactive), and 10% fillings with recurrent caries. No relationship was found between caries prevalence, degree of dependence, number of medicaments, age, and gender, Patients with psychiatric diseases had increased caries prevalence (P<0.01), and lower caries prevalence was associated with frequent tooth brushing (P<0.05). At the tooth level root caries was associated with high plaque scores (P<0.001), degree of gingival recession (P<0.001), presence of coronal caries (P<0.001), and increased pocket depth (P<0.01). The results strongly indicate that oral hygiene measures should be introduced immediately after hospitalization of these patients.