Acridin-9-yl hydrazine upon treatment with various isothiocyanates (RNCS, R = methyl, allyl, phenyl, p-methoxy phenyl, and p-nitro phenyl) yielded the corresponding thiosemicarbazides with acridine substituted on the carbazide-type side. The alkyl-substituted compounds were present in solution as equilibria consisting of the major H-10, H-12 tautomer (either E or Z or both about the C13-N14 bond) and