A series of bis (indolyl) hydrazide–hydrazones 5a–n were synthesized and evaluated for their cytotoxicity against selected human cancer cell lines. The reaction of indole-3- carboxaldehyde 2 with indole-3-carbohydrazide 4 in presence of catalytic amount of acetic acid afforded 5a–n in good yields. Among the synthesized bis (indolyl) hydrazide– hydrazones, the compound 5b with N-(p-chlorobenzyl) and bromo substituents was found ...