The invention provides novel 1- or 2-adamantylmethyl hydrazines of the general formula A ##STR1## In this formula Ad is 1- or 2-adamantyl, R.sub.1 and R.sub.2 are the same or different and are each hydrogen or a lower unsubstituted or substituted alkyl group of 1-4 carbon atoms; R.sub.3 and R.sub.4 are the same or different and are each hydrogen, an unsubstituted or substituted radical being a lower alkyl group of 1-4 carbon atoms a lower alkanoic acid radical of 2-4 carbon atoms or a lower alkyl ester thereof, adamantyl, aryl, aralkyl in which the alkyl moiety has 1-4 carbon atoms or an unsubstituted or substituted heterocyclic radical of aromatic character; or R.sub.3 and R.sub.4 together with the nitrogen atom to which they are attached form a cyclic radical or non-aromatic character.The invention further provides pharmaceutically acceptable acid addition salts of the above compounds.Several methods of preparation of the new compounds are described.The novel compounds according to the invention possess valuable antifungal (human and plant), antiviral, antiprotozoal and antimicrobial properties.