Abstract A number of thiosemicarbazones of 2-acetyl-imidazo [4, 5-b] pyridine were prepared in order to investigate their in vitro antineoplastic activities. Three compounds:(i) 2- acetylimidazo [4, 5-b] pyridin-4-sec-butyl-3-thiosemicarbazone [(A 7), NSC674098],(ii) 2- acetylimidazo [4, 5-b] pyridin-4-tert-butyl-3-thiosemi-carbazone [(A 9), NSC674099],(iii) 2- acetylimidazo [4, 5-b] pyridin-4-cyclohexyl-3-thiosemicarbozone [(A 11), NSC674101] ...