In 2006, several southern states in India reported outbreaks of chikungunya. In the metropolis of Chennai, the first laboratory-confirmed chikungunya cases had an onset of symptoms at the end of May 2006. The authors reviewed surveillance data in which a suspected case of chikungunya was defined as a patient presenting with fever and arthralgia at a medical camp in Chennai on and after June 20, 2006. Over the same period, the authors reviewed surveillance data and larval indices for the vector Aedes aegypti. From June 20 to October 10, 2006, they reported 4,760 suspected cases of chikungunya (attack rate of 0.1%, no fatalities). Control measures included removal of breeding sites, daytime fogging against adult mosquitoes, and information campaigns. The early detection and effective prevention of future outbreaks rely on strengthened human and entomological surveillance, participation of private medical practitioners in case reporting, and community involvement to reduce potential breeding sites of the vector.