Objective: To diagnose parasitic worms during colonoscopy in our patients. There have not been many studies in India which discuss about the presence and the type of parasitic worms present in the colon while doing colonoscopy. Hence this present study was carried out to study about the presence and the type of parasitic worms present in the colon while doing colonoscopy in our institute. Methods: A study of 72 patients who had undergone colonoscopy in our institute for a period of 5 years from November 2009 to October 2014 was carried out in order to find out the presence of parasitic worms during colonoscopy in these patients. Results: Out of these 72 patients, parasitic worm was found in the colon in only one patient. But the stool examination of the patient was negative for ova or cyst. The parasitic worm found in this patient was identified as whipworm or trichuris trichiura by its characteristic whip like shape. In this patient, the tail or the posterior end of the whipworm is straight and bluntly round without any coil or corkscrew shape and hence can be identified as the female whipworm. The tail or the posterior end is highly curved and coiled like a corkscrew only in the male whipworm. Thus, while doing colonoscopy we can easily distinguish between male and female whipworm by looking at the tail or posterior end of the whipworm. But unlike hookworms which suck blood from the small intestinal wall and is red in colour, whipworms do not feed on blood and is white in colour as it feeds only on the tissue secretions of the large intestinal wall. Thus the whipworm in this patient was white in colour. Conclusion: Whipworms are the most common nematodes or roundworms found in the large intestine of human beings while doing colonoscopy. Our patient was also found to have whipworm in the colon while doing colonoscopy. The patient who had whipworm in our study had negative stool examination for ova or cyst. Hence colonoscopy is a very useful investigation to diagnose whipworm infection especially when the stool examination is negative for its eggs.