Background: health condition in children has remarkable effect on oral health. Audiotory limitation in deaf children makes them obtain less information, including information of oral and dental health. Most individuals with deafness have poor oral hygiene compared to that in normal children, making them more vulnerable to caries, particularly on mandibular permanent first molars, since these teeth erupted first, so that they have the longest presence within mouth. Objective: to identify the difference of the number of carious mandibular permanent first molars in deaf and non-deaf children. Methods: analytic observational study using cross-sectional approach from May to June 2009. Population comprised deaf and non-deaf students. Samples were taken using purposive sampling, resulting in 112 samples, each group comprised 56 samples. Materials: nierbecken, sonde, oral mirror, pinset, petri dish, 20% alcohol, cotton roll, cotton pelet, and aquadest. Data analysis was done using Chi-Square test. Result: The number of carious mandibular permanent first molars in deafness group was 24 teeth, while that in non-deafness group was 13 teeth. Chi-Square test revealed difference in the number of carious mandibular permanent first molars in children with deafness and non-deafness. Conclusion: There is difference in the number of carious mandibular permanent first molars in deaf and non-deaf children.