Our objective was to design and synthesize substituted o-carboranes carrying the 1,3,5-s-triazine units as potential boron neutron capture therapy agents. The preliminary results indicated that selective substitution was successful, and the structural AB(2) (mono-o-carboranyl-1,3,5-s-triazine) or A(2)B (bis-o-carboranyl-1,3,5-s-triazine) type was used as the starting point for the generation of biologically active species. In the first series, the influence of the structural changes in the central core unit was investigated. Thus, a procedure for the sequential, selective derivatization of cyanuric chloride that allows for the incorporation of o-carborane was elucidated. As a result, a variety of mono-, di-, and tri-substituted triazines were produced in good yield. In the second series, the effect of additional amine substituents on the 1,3,5-s-triazine was studied. Copyright (C) 2003 John Wiley Sons, Ltd.