Development of novel energetic materials is a significant challenge. Cocrystallization has been explored as another route to development of novel materials. However, very little characterization of detonation performance has been performed for these energetic cocrystals. A major challenge for performing detonation velocity measurements with cocrystals is that typical measurement techniques require hundreds of grams to kilograms of material, an amount that exceeds the entire supply of many cocrystals. In this work, small-scale detonation velocity measurements using about 1.2 g of material per test employing microwave interferometry are presented and discussed for a novel cocrystal of 1-methyl-3,5-dinitro-1,2,4-triazole (MDNT) and hexanitrohexaazaisowurtzitane (CL-20) in a 1:1 molar ratio and compared to a physical mixture of MDNT and CL-20 in the same molar ratio. The results are compared with detonation velocity measurements with cyclotetramethylene tetranitramine (HMX), which provide validation of the technique and further comparison of the results. With this technique, detonation velocity differences as low as 100 m/s are resolvable. The MDNT/CL-20 cocrystal is observed to detonate over 500 m/s faster than the physical mix and over 600 m/s faster than HMX at the same charge density which is held constant in this work. The enthalpy of formation of the MDNT/CL-20 cocrystal was also measured. Using this, the detonation velocity of the cocrystal was calculated using thermochemistry to be 230 m/s faster than that of the physical mixture of MDNT and CL-20 in the same molar ratio as is contained within the cocrystal at a charge density of 1.4 g/cm(3). The higher detonation velocity of the cocrystal (both measured and predicted) compared to the physical mixture is likely attributable to bonding energy contained within the cocrystal and the arrangement of the coformers within the cocrystal.