Cases of dengue fever have been on the rise in the northern part of India over the last decade. Rohtak district of Haryana State in northern India experienced its first large scale outbreak of dengue fever in the year 2006. Out of four serotypes causing dengue fever in the present outbreak, DEN-3 was the predominant serotype. Out of 701 suspected cases of dengue fever, 152 cases (21.7%) tested positive for IgM anti-dengue antibodies and 104 cases (14.8%) for both IgM and IgG anti-dengue antibodies. Fifty per cent of the cases were in the age-group of 11-30 years. We analyzed various contributory factors for the occurrence of the present outbreak. We also identified an important triggering factor, I.e. the inordinate delay in the completion of a rainwater drainage project by civic authorities leading to the collection of rainwater in artificial containers that acted as ideal breeding sites for Aedes mosquito. The present outbreak should serve as an eye-opener for health care authorities as well as the civic administration hoping to prevent future outbreaks in developing countries.