Distinct biological properties of the ortho-carboranyl (1,2-dicarba-closo-dodecaboranyl) glycosides 1, 2 and 3 were evaluated to estimate the suitability of these compounds for cancer treatment by boron neutron capture therapy. The boron uptake into B16-Melanoma cells was significantly higher by incubating the cells with aqueous solutions of carboranyl glucoside 1 (11.2 ppm after 3h), lactoside 2 (13.2 ppm after 12h) and maltoside 3 (20.0 ppm after 24h) compared with solutions of clinically used p-boronophenylalanine (BPA) 5 (3.1 ppm after 24h). Carboranyl maltoside 3 was more effective than boron-10 enriched 5 in killing C-6 rat glioma cells by incubating the cells with the compound and subsequent treatment with thermal neutrons. 3 was also administrated iv, in concentrations of 25 mg boron/kg body weight to rats bearing brain tumors. After a period of 4h after administration the concentration of boron in the tumor tissue was 3.0 ppm.