C. N. O'Callaghan and Dermot Twomey, of the Medical Research Council of Ireland, Trinity College, Dublin, have described the preparation and properties of fris-hydrazides and related compounds (Proceedings of the Royal Irish Academy, 63, Section B, No. 12: Anti-tubercular Substances; 19: The Preparation and Properties of bis-Hydrazides and Related Compounds. 1964. Is. 6d.). Since the discovery of the anti-tuberculosis properties of isoniazid, considerable attention has been directed to the preparation of compounds containing hydrazide groupings. Apart from mono-hydrazides, anti-tuberculosis properties have also been ascribed to various bis -hydra -zides and structurally related compounds. One of the latter, cyanoacetohydrazide, has been thoroughly examined; despite conflicting reports, it is now generally considered to be much less active in vivo than isoniazid. A feature of compounds such as ethyl malonate, ethyl cyanoacetate and ethyl acetoacetate, which contain a reactive methylene group, is the ease with which they undergo the well-known Knoevenegel reaction with aldehydes and ketones to yield a series of compounds of type I, where R is CO2Et, CN and COCH3, respectively. The reaction of these condensation products with hydra-zine has been investigated.