The utility of hydrazonoyl halides as precursors in synthesis of numerous biologically active compounds is presented. The biologically active compounds, that have been covered, include lipogenase, lipoxygenase and cyclo-oxygenase inhibitors, antiinflammatories, phytotoxic agents, herbicides, acaricides and miticides, insecticides, weed controlling agents, antimicrobial agents, central benzodiazepine receptors, antitumors, antagonistic agents, analgesics and anticonvulsant agents.