Caries is not the consequence of a single event but it is rather a sequel of a series of processes happening over a longer period of time. The etiological factors which can be diagnosed today, that is, the risk of caries, do not necessarily have to be identical with the causative factors which led to the development of a carious lesion. In scientific studies various so-called ‘predictors’ for the risk of caries have been investigated. These could be clinical signs of caries or risk indicators, such as factors associated with the development of caries. Their effects on the development of caries can be either causative or modifying. Causative relationships are often identified as risk factors. An individual with an increased risk of caries may, therefore, be a person with a higher than average exposure to the causative risk factors mentioned below. Several studies have attempted to determine risk factors that can be reliably used to assess the level of risk of caries progression in individual patients. It has been established that high-risk patients include those who have a high bacterial challenge, which may consist of a combination of high numbers of mutans streptococci, lactobacilli or both. Accurate detection of early caries can increase the reliability of caries risk assessment, particularly if those measurements are made at three or six-month intervals and caries progression can be measured. This chapter incorporates various factors relevant to caries risk assessment in detail. It also includes a brief description of cariogram which is an interactive version for estimation of dental caries.