Background: Homoeopathy as a system of medicines & that deals with any disease condition in a holistic way brings to the needs of present scenario which possesses a better scope to reduce the recurrency of disease. Susceptibility is revealed by the reaction that occur when the host interacts with environmental factors by the sign and symptoms.  Respiratory tract infections is spreading rapidly within the communities & represent the third most frequent health problem across the globe due to microorganism. The disease is vulnerable to infection than the other parts of body. The intensity of symptoms can be ranged from mild to severe. Most of the incidence is underestimated because of infection are mild & not hampers the daily activities until severity. According to WHO data published in 2017 death in India due to RTI (i.e. lung disease) reaches 8, 96, 77 or 10.19% which India ranks 4th in the world & adolescent & adults have approximately 2-4 cold in a year. By assessing the susceptibility and proper selection of potency of simillimum can bring an ideal cure. The study was to understand the concept of susceptibility and its application in RTI disease. Aim and Objective: The aim of the study is to review on the available literature with objective to subject each research paper in order to shed light on the current topic and to find the way for new research. Methods: Databases such as PubMed, Google Scholar, Medline and Science Direct were used to search the articles. CONCLUSION: This study suggested that the importance of assessment of Susceptibility in Homoeopathy which helps in evaluation of cases and selection of potency and the curative dose of simillimum. As Homoeopathic medicine gives effectively relief to the patient and restoration of the normal susceptibility is the basis of cure. KEYWORDS:  Homoeopathy, RTI,  Susceptibility, Simillimum