BACKGROUND the Mini Nutritional Assessment (MNA) is a multidimensional method of nutritional evaluation that allows the diagnosis of malnutrition and risk of malnutrition in elderly people, it is important to mention that this method has not been well studied in Brazil. OBJECTIVE to verify the use of the MNA in elderly people that has been living in long term institutions for elderly people. DESIGN transversal study. PARTICIPANTS 89 people (>/= 60 years), being 64.0% men. The average of age for both genders was 73.7 +/- 9.1 years old, being 72.8 +/- 8.9 years old for men, and 75.3 +/- 9.3 years old for women. SETTING long-term institutions for elderly people located in the Southeast of Brazil. METHODS it was calculated the sensibility, specificity, and positive and negative predictive values. It was data to set up a ROC curve to verify the accuracy of the MNA. The variable used as a "standard" for the nutritional diagnosis of the elderly people was the corrected arm muscle area because it is able to provide information or an estimative of the muscle reserve of a person being considered a good indicator of malnutrition in elderly people. RESULTS the sensibility was 84.0%, the specificity was 36.0%, the positive predictive value was 77.0%, and the negative predictive value was 47.0%; the area of the ROC curve was 0.71 (71.0%). CONCLUSION the MNA method has showed accuracy, and sensibility when dealing with the diagnosis of malnutrition and risk of malnutrition in institutionalized elderly groups of the Southeastern region of Brazil, however, it presented a low specificity.