Objective: Severe anaemia is reported to occur in severe hookworm infection in many studies. But so far detailed study was not done to know about the occurence of severe anaemia and its relation with stool examination for hookworm ova in patients with severe hookworm infection. Hence a detailed study was done to know about severe anaemia and its relation with stool examination for hookworm ova in patients with severe hookworm infection found while doing upper gastro intestinal endoscopy in our institute. Methods: A study of 1100 patients who had undergone upper gastro-intestinal endoscopy for a period of four and half years from May 2009 to October 2013 was carried out in our institute. In each of these 1100 patients, the first and second part of duodenum were carefully examined to find out the presence of hookworms. In all the patients found to have hookworms in duodenum, investigations were done to know about the presence of anaemia except in the very few patients who were lost for follow up. In patients with severe anaemia [haemoglobin __ampersandsignlt;7g/dl or g%] stool examination was done to look for the presence or absence of hookworm ova. The results were found as given below. Results: Out of these 1100 patients, as many as 18 patients were found to have hookworms in duodenum while doing upper gastro-intestinal endoscopy. Out of these 18 patients, 4 patients were lost for follow up and full details about their investigations were not available. The remaining 14 patients were taken into consideration for our study. Out of these14 patients, 9 patients had anaemia and 2 of these 9 patients were found to have severe anaemia [haemoglobin __ampersandsignlt;7g/dl or g%]. Severe anaemia indicates significant loss of blood which will occur only due to heavy burden of hookworms in severe hookworm infection. Hence severe anaemia is suggestive of severe hookworm infection due to heavy burden of hookworms. But in both these patients, stool examination was negative for hookworm ova despite a heavy burden of hookworm infection with severe anaemia. Conclusion: Thus even a heavy burden of hookworm infection with severe anaemia can present with negative stool examination for hookworm ova. Hence upper gastro intestinal endoscopy should be done to confirm the presence of hookworms in all patients with anaemia even when stool examination is negative for hookworm ova.