OBJECTIVES: Self-report is the "gold standard" for pain assessment, however, observational pain scales, such as Doloplus-2 must be used for patients who cannot communicate. In this follow-up study, we report the psychometric properties of the observational Doloplus-2 scale using the visual analog scale (VAS) pain score as a gold standard and evaluate its performance. METHOD: Prospective clinical study of 180 hospitalized older patients who demonstrated good comprehension and reliable use of the VAS: 131 participants with dementia and 49 without. All participants assessed their chronic pain using the VAS. Doloplus-2 was independently completed by the nursing team. RESULTS: Mean age of patients (133 women, 47 men) was 83.7+/-6.5. Median mini-mental state examination of patients with diagnosis of dementia was 18.0+/-7.7. Nearly half of the patients (49%) reported that they experienced pain in response to a direct question. The administration of Doloplus-2 was possible in all 180 patients. Doloplus-2 correlated moderately with self-assessment (Spearman coefficient: 0.46). In a multiple regression model, Doloplus-2 predicted 41% of the variability in pain intensity measured by VAS. The somatic dimension alone explained 36% of the variance, the psychosocial bloc 5% with no better contribution of the psychomotor bloc. To shorten Doloplus-2, we constructed a version with only the 5 items that were significantly associated with the VAS score in the multiple regression models. DISCUSSION: The observational Doloplus-2 scale correlates moderately with self-assessment pain score and has adequate internal consistency. Our data also suggest that Doloplus-2 could be substantially shortened as the brief version performed similarly to the complete Doloplus-2.