Antimycobacterial effects of thiosemicarbazones were discovered in the late 1940s. The best known representative of these compounds is thioacetazone that has been used in the therapy of tuberculosis since the turn of the 1940s and 1950s. At present, it is used only rarely since it exhibits severe side effects. This paper deals with the antimycobacterial effects of thiosemicarbazones and N,N-dimethylthiosemicarbazones derived from 5-alkyl-2-acetylpyrazines. Some of these compounds displayed high inhibition of the growth of Mycobacterium tuberculosis H37Rv, but were excluded from the in vivo studies due to their cytotoxic effects. Nonetheless, they can be used as model compounds for studying the mechanisms of antimycobacterial action of thiosemicarbazones.