The invention relates to nitrosourea derivatives, a process for their preparation and pharmaceutical compositions containing them.The nitrosourea derivatives of the invention correspond to the following formula (I): ##STR1## in which: R can represent a hydrogen atom or an alkyl group from 1 to 30 carbon atoms, X represents a hydroxy group or an -NR.sub.1 R.sub.2 group, Y represents a hydrogen atom, a hydroxy group or an -NR'.sub.1 R'.sub.2 group, where R.sub.1 and/or R'.sub.1 each represent a hydrogen atom or a ##STR2## group, Hal being a halogen, and R.sub.2 and/or R'.sub.2 can each represent a hydrogen atom or an alkyl group comprising from 1 to 6 carbon atoms, R' and R" can represent hydrogen or OH, provided that at least X represents ##STR3## with R.sub.1 representing ##STR4## or Y represents ##STR5## with R'.sub.1 representing ##STR6## and provided that either R' represents hydrogen or R" represents hydrogen, and R' and R" cannot be simultaneously hydrogen atoms.These compounds present an antitumor activity.