Circulating filarial antigen (CFA), determined with Og4C3 ELISA, is a marker of Wuchereria bancrofti adult worm infection. The reduction of CFA over 2 years was determined in 185 microfilaremic and 111 amicrofilaremic but CFA+ adults given an annual dose of either diethylcarbamazine (DEC) or ivermectin or the two combined. Reduction of CFA level was good with DEC but weak with ivermectin and followed the same pattern in amicrofilaremic and microfilaremic groups. Combinations and DEC alone had a similar impact on CFA level. CFA clearance was observed in amicrofilaremic but not in microfilaremic persons in all DEC-containing treatments. However, the highest clearance rate was observed in persons treated with DEC at 6 mg/kg combined with ivermectin. Continuous reduction of CFA level after repeated treatments shows that elimination of W. bancrofti infection, monitored by CFA clearance, might be achieved within a few years with annual treatments of DEC combined with ivermectin.