UNLABELLED: Visual assessment of surfaces may not be enough to document the level of cleanliness in the hospital setting. It is necessary to introduce quantitative methods to document the results of this practice. OBJECTIVE: To evaluate the efficacy of hospital terminal cleaning procedures, using an adenosine triphosphate (ATP) bioluminescence method in a teaching hospital. METHOD: During 2008 we conducted an evaluation using ATP bioluminescence LIGHTNING MVP (Arquimed) of external and internal housekeeping service. After conducting an initial evaluation we implemented education of cleaning practices and finally we did a post intervention evaluation. Using chi-square method we compared prior versus after cleaning, quality of cleaning performed by external versus internal personnel, single versus double terminal cleaning procedures and prior versus after intervention. A finding of three RLU or less was considered a clean surface. RESULTS: We performed 198 evaluations in 33 patient units and nine OR. Internal personnel accomplished 25.37% of clean surfaces before and 80% after the education intervention (p=0.01). In contrast, external personnel obtained 68.8% before and 73.33% after intervention (p=0.3). CONCLUSIONS: This study suggests that visual assessment is not enough to ensure quality of the process and it is necessary to document the level of cleanliness by quantitative methods.