Aims: To conduct a prospective, community based study in an impoverished urban site in Kolkata (formerly Calcutta) in order to measure the burden of cholera, describe its epidemiology, and search for potential risk factors that could be addressed by public health strategies. Methods: The study population was enumerated at the beginning and end of the study period. Surveillance through five field outposts and two referral hospitals for acute, watery, non bloody diarrhoea was conducted from 1 May 2003 to 30 April 2004. Data and a stool sample for culture of Vibrio cholerae were collected from each patient. Treatment was provided in accordance with national guidelines. Results: From 62 329 individuals under surveillance, 3284 diarrhoea episodes were detected, of which 3276 (99% ) had a stool sample collected and 126 (4% ) were culture confirmed cholera. Nineteen (15% ) were children less than 2 years of age, 29 (23% ) had severe dehydration, and 48 (38% ) were hospitalised. Risk factors for cholera included a household member with cholera during the period of surveillance, young age, and lower educational level. Conclusions: There was a substantial burden of cholera in Kolkata with risk factors not easily amenable to intervention. Young children bear the brunt not only of diarrhoeal diseases in general, but of cholera as well. Mass vaccination could be a potentially useful tool to prevent and control seasonal cholera in this community. Aims: To conduct a prospective, community based study in an impoverished urban site in Kolkata (formerly Calcutta) in order to measure the burden of cholera, describe its epidemiology, and search for potential risk factors that could be addressed by public health strategies. : The study population was enumerated at the beginning and end of the study period. Surveillance through five field outposts and two referral hospitals for acute, watery, nonblood diarrhoea was conducted from 1 May 2003 to 30 April 2004. Data and a stool sample. For culture of Vibrio cholerae were collected from each patient. Treatment was provided in national with national guidelines. Results: From 62 329 individuals under surveillance, 3284 diarrhoea episodes were detected, of which 3276 (99% ) had a stool sample collected and 126 ( 4%) were culture confirmed cholera. Nineteen (15%) were children less than 2 years of age, 29 (23% ) had severe dehydration, and 48 (38% ) were hospitalised. Risk factor s for cholera included a household member with cholera during the period of surveillance, young age, and lower educational level. Conclusions: There was a substantial burden of cholera in Kolkata with risk factors not easily amenable to intervention. Young children bear the brunt not only Of diarrhoeal diseases in general, but of cholera as well. Mass vaccination could be potentially useful tool to prevent and control the seasonal cholera in this community.