A population from a W. bancrofti- endemic area was evaluated by use of microfilaria(Mf) and adult worm circulating antigen(CAg) enzyme linked immunosorbent assay to demonstrate the relation of these two parameters to age , gender and the clinical status (symptomatic or asymptomatic) of the examined individuals. In addition, antigen-driven T cell proliferation was measured to study the effect of the clinical status and / or infection status on the host responsiveness in lymphatic filariasis. The results showed that the prevalence rates of each of the two markers are clearly age dependent and were significantly higher in males than females. The antigen prevalence rate was consistently higher than the microfilaria prevalence rate in all age groups. Among the asymptomatic and symptomatic patients, the direct relationship between Mf+ and CAg+ remained intact regardless of clinical status. Individuals positive for CAg had significantly lower lymphocyte proliferation responses to parasite antigen than did CAg-negative people. This study re-emphasizes the importance of CAg measurements for accurately assessing the clinical status of filariasis and demonstrates that the presence or absence of active infection, not clinical status is most closely associated with the immune responsiveness in lymphatic filariasis.