Abstract: The present invention relates to novel aminoalkyl substituted nitrosourea derivatives as well as their acid addition salts with pharmaceutically acceptable acids showing pronounced antineoplastic effectiveness in animal experiments.The novel compounds of the present invention may be represented by the following formula: ##STR1## wherein X and Y are the same or different, and are selected from the group consisting of a phenyl group and a cyclohexyl group, said phenyl and cyclohexyl groups being optionally substituted with one or two substituents selected from a halogen atom, a lower alkyl group having from one to four carbon atoms inclusive, a trifluore methyl group, a cyano group, a phenyl group, a cyclohexyl group and a lower alkyloxy group having from one to four carbon atoms inclusive."Alkylene" is an alkylene group, branched or unbranched, having from one to four carbon atoms inclusive, and R.sup.1 and R.sup.