Apical periodontitis is a group of inflammatory diseases caused by microorganisms infecting the necrotic root canal system. The pathogenesis of different types of apical periodontitis and even the same type in different individuals is unlikely to follow a stereotyped fashion with regard to the involved bacterial mediators. Apical periodontitis starts as local inflammation in the periodontal ligament and when untreated can lead to larger destruction of the periapical tissues. The study was aimed to find if there was an association between failed root canal treatment and systemic diseases. Data was collected retrospectively from the records of the private dental college. The population included in the study were the patients who reported with failed root canal treatment. Descriptive statistics, Cross tabulation and chi square test were done. The most common systemic disease in the patients’ undergoing retreatment was diabetes. There was no significant association between gender and the systemic diseases. General health condition of a patient may influence the healing periapical lesions and therefore the outcome of the root canal treatment. Both systemic and tooth related factors can have a negative impact on the success of endodontic treatment.