Indices used to evaluate plaque accumulation and coronal caries have been widely accepted in epidemiological studies, yet their reliability cannot be guaranteed. The aim of this study was to evaluate the reliability of clinical criteria used in coronal and root caries diagnosis and oral hygiene evaluation as applied in elders. Nineteen elderly subjects, 73 years old on average, were examined at a first appointment by two independent examiners. They were re‐examined two weeks later. Plaque accumulation was evaluated using the Plaque Index (PI) and coronal and root caries were detected according to the WHO criteria and Fejerskovet al(1991), respectively. Recurrent caries was recorded as recommended by WHO and by probing at the interface tooth‐restoration. Inter‐ and intra‐examiner agreement was evaluated using kappa statistics. The PI score showed good reliability except for examiner b, for whom a simplification of the 4‐point scale in 3‐point scale improved significantly the reliability. The prevalence of coronal caries was very low and intra‐ and inter‐examiner agreement was poor. Most of the root caries lesions were covered by plaque and the kappa values indicated only poor agreement. Recurrent caries were found with good agreement using WHO criteria but the detection with the probe was not reliable. In conclusion, it seems that examiners should be trained carefully to maximise their reliability and that plaque should be removed to obtain reliable diagnoses of caries. Retraining and calibration may be necessary for surveys continuing ove