Journal of Medical Primatology, 2014; 43 (2014): 144-152Background: The ring-tailed lemur (Lemur catta) is a quadruped arboreal primate primarily distributed in south and south-western Madagascar. This study was carried out to describe the normal radiographic thoracic anatomy of the ring-tailed lemur as a reference for clinical use. Methods: Radiography of the thorax was performed in 15 captive ring-tailed lemurs during their annual health examinations. Results: Normal radiographic reference ranges for thoracic structures were established and ratios were calculated, such as the vertebral heart score (VHS). The mean VHS on the right lateral and dorsoventral views was 8.92 ± 0.47 and 9.42 ± 0.52, respectively. Conclusions: Differences exist in the normal radiographic thoracic anatomy of primates. Knowledge of the normal radiographic thoracic anatomy of individual species is important and fundamental to assist in clinical cases and for accurate diagnosis of diseases.