The Widal test was done in 100 nontyphoidal febrile pients, 53 patients with proven typhoid, and in 61 patients with immunological disturbances in an are where typhoid is endemic. Salmonella typhi H or O agglutinin titers of 1:160 or more were seen in only 1% of nontyphoidal fevers. Using these criteria, the Widal test was of diagnostic value in 50 of 53 (94.3%) of patients with typhoid. The Widal test was positive in 85.7% of patients even in the first week of the illness, possibly owing to the hyperimmune state of the patients. A false-positive test was found in 11.5% of patients with major immunological disturbances in whom the Widal test must therefore be interpreted with caution.