Having close kinship to Brugia malayi, B. pahangi is a member of the family Filariidae, which causes lymphatic filariasis in dogs and cats. Although this nematode is unlikely to cause a zoonotic disease in humans, study of the B. pahangi life cycle may help control human filariasis. The objective of this study was to examine microfilarial rates and densities of B. pahangi in experimentally induced infections in cats as a relative measurement. Cats were infected with 3 different amounts of 3rd-stage larvae (L3); 100, 300 and 500. Cats infected with 100 L3 became patent for microfilariae longer than the other groups (mean100 = 99+/-44 days). In comparison, the pre-patent period of B. pahangi was somewhat shorter in cats with 300 and 500 L3 infections (mean300 = 76+/-13 and mean500 = 63+/-5 days). The microfilarial densities of these cats were also determined; the density of microfilariae (mf/1 ml blood) increased relative to the duration of infection. One-way ANOVA tests were used to compare the microfilarial densities of the cats with varying numbers of L3. We found that the microfilarial density of cats with 500 L3 exhibited significant differences (p < 0.05) from cats with 300 and 100 L3. However, we concluded that the amount of microfilariae produced in the blood circulation of these cats were not increasing relative to the numbers of L3 taken by the host.