Introduction: The poor oral hygiene (OH) among institutionalized elders and consequent accumulation of bacterial plaque may lead to an increased risk for developing oral pathology and also other conditioning situations of systemic health. Objectives: OH evaluation conditions in an institutionalized elder population and determination of bacterial plaque presence. Material and Methods: Observational, cross-sectional, descriptive study, with 372 individuals 60+ years old residents in 22 homes of the Porto District, randomly selected (clusters).Descriptive/inferential analysis using SPSS©vs.17.0 (α=0.05). Multivariable logistic regression (backward stepwise method, p=0.05/p=0.10 for factor inclusion/exclusion). Results: Mean age was 78.8(± 9.1) years, 69.9% women, 30.4% had no schooling and 81.7% were completely independent regarding OH procedures. 38.9% did not brush their teeth. Gender and independence degree were related to the number of daily brushings; age has not shown this relationship. 71.1% do not brushed and said "do not need to do". The plaque index of Silness and Löe, presented average value of 2.2(±0.76) and 4(1.7%) elders were registered with no bacterial plaque. From the multivariate analysis it was concluded that the presence of visible bacterial plaque is associated only with the number of brushings performed. Conclusions:The oral health conditions observed are relevant to invest on preventive programs with a base of information addressed to the populations. Clinical Implications: The evidence does lead us to state that, in these populations, there is an increased need to control the bacterial plaque therefore preventing the risk of associated pathology. Palabras clave: oral hygiene, plaque index, daily brushings, bacterial plaque, oral health, institutionalized elderly