A filariasis survey was carried out for the first time in the Little Andaman island, covering a population of 12,247 in 12 of the 13 villages. Infection due to Wuchereria bancrofti was found only in 3 villages with microfilaria (mf) rate ranging from 1.02 to 6.45 per cent. Observations on the appearance of mf in peripheral blood showed that the parasite is nocturnally periodic form with a peak at 2000 h. The infection was prevalent only among the settlers from Bihar and Bangladesh and none of the local tribal population was affected. Carriers included 18 males and 4 females. Their age ranged from 6 to 50 yr. Only one of 2788 individuals examined was found to have clinical manifestation. A total of 442 female mosquitoes belonging to eight species were collected and dissected. Natural infection was found only in Culex quinquefasciatus (0.24%). Epidemiological investigations and vector studies indicates local transmission. Thus, this island appears as a new focus of infection.