Filariasis, one of the parasitic diseases, is an important health problem in tropical and sub-tropical countries. The parasitic filarias found in Thailand are Brugia malayi and Wuchereria bancrofti. These worms are the cause of filariasis or elephantiasis of which there are endemic areas in the southern and westhern part of Thailand. At present, there are many foreign workers from neighboring countries immigrating to Thailand. Some of them are carriers of filariasis that may transmit to Thai people and lead to a public health problem.