31 children were examined in this pilot study. They were between 11-13 years old and had at least one permanent second molar present. Status of oral hygiene (TURESKY modification of the QUIGLEY and HEIN plaque index, QHI, and Approximal plaque index, API), the gingivitis index (Papillary bleeding index, PBI), Status of caries (DMFS/dmfs), and values of ClinproTM Cario Diagnosis were recorded. Data analysis was accomplished using Kappa test (SPSS 10.0). We did not observe any good correlation between ClinproTM Cario Diagnosis and Caries lesions, nor between ClinproTM Cario Diagnosis and oral hygiene indices. These results suggest that ClinproTM Cario Diagnosis was not suitable for indication of caries and that it was different from oral hygiene indices.The study was supported by 3M ESPE. Keywords: QHI, API, lactic acid, caries risk, oral hygiene