Novel hydrazones derived from 3-formylrifamycin S or SV as the aldehydo component and a bi- or tri-cyclic N-aminopiperazine as the hydrazino component and having the formula ##STR1## in which R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6, independently of one another, each represents a hydrogen atom or C.sub.1-4 -alkyl,m and n, independently of one another, each represents an integer from 0 to 5,X represents C.sub.1-5 -alkylidene, benzylidene or C.sub.1-4 -alkoxymethylene,Y represents C.sub.1-5 -alkylidene, C.sub.1-4 -alkoxymethylene, oxy, thio or optionally substituted imino of the formula --N(R)-- wherein R represents hydrogen, C.sub.1-4 -alkyl, C.sub.3-5 -alkenyl, C.sub.3-12 -cycloalkyl or phenyl, orX and Y together represent 1,2-cycloalkylene or o-phenylene each of which can be substituted by from one to three C.sub.1-4 -alkyl radicals, andRif represents a radical of rifamycin S or SV that is bonded in the 3-position by the free valency,are distinguished by a high and long-lasting antituberculotic activity. They are manufactured in conventional manner, for example by condensation of their components.