The design, synthesis and antituberculosis activity of a series of 2-aryl-5-methylthio-1,3,4-thiadiazoles (5a-b), ethyl alpha-(5-aryl)-1,3,4-thiadiazole-2-ylthio)acetates (8a-b) and related compounds are described. All of the compounds were tested against Mycobacterium tuberculosis strain H37Rv in comparison to rifampicin. Six compounds exhibited a very good activity (MIC < 6.25 micrograms/ml, % Inhibition = 100).