The present study entitled 'An estimation of caries susceptibility in medically compromised child patients' was carried out in the Department of Pedodontics and Preventive Dentistry, Faculty of Dental Sciences, Chatrapati Shahuji Maharaj Medical University, Lucknow, in collaboration with Department of Pediatrics, Chatrapati Shahuji Maharaj Medical University, Lucknow, to assess the caries susceptibility in diseased child patients. Total one hundred and eleven patients were examined. Amongst them forty were controls and seventy one were diseased patients. The diseased children of both sexes were selected between age 3 years to 14 years, and analyzed mainly on the basis of two parameters I)Medications they are taking II)Form of the disease i.e. with or without chronic debilitating diseases. Control group children were selected who are not taking any kind of syrups/medicines and without obvious carious lesions/ filled surfaces / extraction. Every child's caries susceptibility was checked using Oratest after taking the consent from their parent. General information along with a questionnaire was recorded for each child in separate sheets and analyzed statistically.