The nuclease activity of the oxo-peroxo molybdenum (VI) complex on DNA has been studied by UV-Vis, fluorescence, viscosity, and gel electrophoresis techniques whereby the complex has been found to promote cleavage of pUC19 DNA from the supercoiled form I (SC) to nicked circular relaxed form II (NC). The intrinsic binding constant of the complex with DNA was calculated and found to be (5.3 +/- 0.02) x 10(5) M(-1) from UV-Vis studies. Fluorimetric studies indicate that the complex competes with EB in binding to DNA. The relative viscosity of CT DNA increases with increasing Mo complex indicating intercalative binding. All the above results suggest that the complex binds to DNA intercalatively and imparts DNA cleavage.