The surface features of microfilaria, third-stage larva and adult of B.malayi and B. pahangi and third-stage larva of W. bancrofti were examined by scanning electron microscopy. It was revealed that the following characteristics can be used for the differentiation of the parasites. The sheat of microfilaria of B. pahangi is granular whereas that of B. malayi is translucent and rather smooth. In the third-stage larvae, the ventrolateral papilla in Brugia has an indentation around its base while this indentation is absent in Wuchereria

and that it is wider in B. malayi than in B. pahangi. Futhermore, the ventrolateral papillae of Burgia has round shape and those of B. malayi are more protruded and bigger than that of B. pabangi, while the shape of these papillae in W. bancrofti are bubble-like. Ribbons of longitudinal folds on the surface annulations are found on the entire body surface in third-stage larvae of W. bancrofti, while they are oresent over some part of the surface in Brugia. Besides, a small papilliform processes on the left side of posterior region is only found in third-stage larya of Brugia and absent in W. bancrofti. In the adult male parasites, the distinguishing feature that can be used is that the tip of the long spicule of B. malayi is spatulate whereas that of B. pahangi is tapered. In the female B.malayi has more numerous tubercles on the surface of the posterior region than in B. pahangi, and that most of these tubercles are larger in size.