Objective: To describe the rate of the caries and the relationship betwwen caries and knowledge, attitude and clinical practises about oral hygiene of the pupils in the secondary school in Buon Ma Thuot city, Dak Lak province in 2012. Methodology: Crosssectional descriptive method was used during interview and clinical exam. Result: The percentage of the pupils with caries is 22.3 percent, the percentage of femal is 24.1 percent and male is 20.8 percent. About knowledge, there is 35 percent with the knowledge about Brass method, 25.8 percent with the right general knowledge about brushing teeth, 54 percent supposed to go to the dentist when having a oral problem, 3.4 percent absolutely not know when the authors should have the periodic oral exam, 82.9 percent having the right knowledge about the effect of fluorine, 37 percent not know what is the gingival and 6 percent think that a perodical oral exam cost money. About clinical problem, 42 percent used method of brushing teeth in horizontal, 20.1 percent used the Brass method, 23 percent having no any fix method, 14 percent brushing teeth right after every main meal, 15 percent going to the dentist in the last 6 months, 65 percent never going to the dentist, 10 percent going to the dentist more than once in a year, 70.2 percent consuming food with sugar once to twice in a day, 62 percent consuming beverage with sugar and 57 percent consuming sweet food. There is the relationship between khowledge, attitude and clinical practise in taking care of teeth in caries patients.