New cytostatic compounds based on isocyanuric acid derivatives having 2 or 3 epoxide group containing substituents on ring nitrogen atoms, of which at least one differs from a glycidyl, having the formula ##STR1## wherein Oxiranyl is the same or different and has the formula ##STR2## wherein R.sub.1, R.sub.2 and R.sub.3 are the same or different and members selected from the group consisting of hydrogen, alkyl, haloalkyl, hydroxyalkyl and alkoxyalkyl and n in an integer from 1 to 8, with the proviso that if n is 1 in all oxiranyl groups, at least one of R.sub.1 or R.sub.3 is other than hydrogen, and R is a member selected from the group consisting of oxiranyl as defined above, hydrogen, alkyl, alkenyl, hydrocarbon aryl, hydrocarbon aralkyl, hydrocarbon alkaryl, cycloalkyl, and cycloalkenyl, optionally containing substituents.When R.sub.1, R.sub.2 and/or R.sub.3 denote alkyl or substituted alkyl in the oxiranyl radical, the alkyl radicals preferably have from 1 to 4 carbon atoms. The total number of carbon atoms in one oxiranyl radical should not be more than 10. The preparation of these compounds by introducing oxiranyl groups of Formula II and the radical R in known manner into the isocyanuric acid ring is also claimed.