Diagnostic endoscopy has proven to be an important diagnostic tool for minimally-invasive visualization and biopsy of internal structures in a variety of species. In reptile medicine, the lack of pathognomonic clinical signs, variable hematology and inconsistent plasma biochemistry results, make disease diagnosis challenging. In many cases reaching a definitive diagnosis relies upon biopsies for histology and microbiology. The ability to explore the coelom and collect biologic samples with targeted precision and minimal trauma using a small diameter rigid telescope with intergrated sheath and operating channel offers a significant diagnostic advantage over surgical coeliotomy or ultrasound-guided techniques. This review describes available equipment, approaches and techniques for examination of coelomic viscera for members of the Squamata, Crocodilia and Chelonia. Emphasis is placed upon the 2.7 mm telescope system as this size is suitable for the majority of reptile species; however, 5 and 10 mm equipment for larger species is also described.