Treatment of typhoid fever with furazolidone produces a high cure rate. This is a clinical curiosity, as furazolidone is described to be poorly absorbed. The present study examined whether furazolidone could produce unequivocal clinical response and, if so whether this was due to the drug producing bactericidal levels in the serum. Twenty one patients selected by defined criteria were treated with furazolidone and evaluated for definite clinical response in 5-7 days. Bactericidal activity of pre dose and post dose sera were estimated in seven patients showing definite clinical response. All the seven patients had a clinical cure without the drug producing significant bactericidal levels in the blood. Hence we concluded that the major site of action of furazolidone was in the intestine. It is our postulate that the organisms reaching the intestine in large numbers from bile are prevented from gaining re-entry into the circulation by the action of furazolidone in the intestine. After repeated cycles of entry of organisms into the intestine from bile and the simultaneous prevention of its re-entry into the circulation, the number of organisms remaining in circulation comes down considerably, thus helping the immune system to bring about a cure.