Synnematin was found by Gottshall and co-workers in 19511and separated into synnematin A and synnematin B by Olson and co-workers in 1953.2Mice were freed of Salmonella typhi and Salmonella typhimurium and chicks of Salmonella pullorum by treatment with synnematin B.3Olson and Holt demonstrated that synnematin B was not toxic for human beings,4and Olson found that synnematin B was effective against a wide variety of Salmonella strains in vitro.5Olarte and Figueredo tested five antibiotics against 40 strains of S. typhi in vitro and found synnematin B to be the most effective.6On the basis of these observations we decided to evaluate synnematin B in the treatment of typhoid in human patients. This is a preliminary report of the first clinical trial of this antibiotic in human beings. SELECTION OF CASES AND CONTROLS An attempt was made to select early, uncomplicated