Niridazole (Ambilhar) was used in the treatment of 20 patients with typhoid fever. The drug was effective in 11 patients. They became afebrile within 5.5 ± 1.5 days. Patients who did not respond were then treated with chloramphenicol and became afebrile within 4.4 ± 10 days. One patient developed a severe drug rash while minor side effects, e. g. headache, nausea, vomiting and aches and pains all over the body, were observed in 4 other patients. The therapy of typhoid fever with niridazole is inferior as compared to chloramphenicol. In vitro niridazole sensitivity tests were carried out in 40 strains of S. typhi and 10 of S. paratyphi which also included the strains isolated in this study. By both disc-diffusion and tube-dilution methods, niridazole was sensitive in concentrations of 20 μ g/disc or 20 μ g/ml.