AbstractThe synthesis and spectroscopical data of 1,2,6‐thiadiazine 1,1‐dioxides, designed as antiprotozoal agents, are reported. Thein vitrotrichomonacidal and trypanocidal activities of new compounds and their precursors were evaluated againstTrichomonas vaginalisandTrypanosoma cruzi. The chemoprophylactic activity on mice treated with blood infected withT. cruziand their mortality percentage were tested. Compounds 2 and 8b show a higher chemoprophylactic activity and lower mortality percentage than Nifurtimox used as reference d