Objective: Eosinophilia occurs very commonly in hookworm infection. But so far detailed study was not done to know about the occurrence of hypereosinophilia in various grades of hookworm infection with or without anaemia. Hence a detailed study was done to know about the occurrence of hypereosinophilia in various grades of hookworm infection found in patients while doing upper gastro-intestinal endoscopy in our institute. Methods: A study of 1259 patients who had undergone upper gastro-intestinal endoscopy for a period of 5 years from May 2009__ampersandsignnbsp;to April 2014 was carried out in our institute. In each of these 1259 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 or absence of hypereosinophilia and anaemia except in the very few patients who were lost for follow up. The results were found as given below. Results: Of these 1259 patients, as many as 18 patients were found to have hookworms in duodenum while doing upper gastrointestinal endoscopy. 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. Of these14 patients, as many as 10 patients were found to have eosinophilia(71%). Severe eosinophilia or hypereosinophilia was found in 4 out of 10 patients with eosinophilia(40%).3 out of 4 patients with hypereosinophilia with hookworm infection in our study had anaemia, but one patient with hypereosinophilia did not have anaemia. Conclusion: Hence, hypereosinophilia is an extremely important indicator of hookworm infection with or without anaemia. Hence upper gastro-intestinal endoscopy should be done to confirm the presence of hookworms in all patients with hypereosinophilia even when there is no anaemia in tropical and subtropical countries.