Isotope dilution mass spectrometry is an ideal analytical technique to measure the elemental abundance of Mo in C1 carbonaceous chondrites and the metallic and troilite phases of iron meteorites. The mean abundance of Mo in two C1 meteorites is 0.909+/-0.040 microg/g which corresponds to a value of 2.55 atoms Mo with respect to Si equal to 10(6) atoms, which is identical to the currently accepted solar system abundance. The partitioning of Mo between the metallic and sulfide phases in the Mundrabilla iron meteorite was found to be 6.0+/-0.2 microg/g and 8.6+/-0.3 microg/g, respectively. A new, precise Mo concentration of 1.54+/-0.04 microg/g for the Geochemical Reference Standard BCR-1 is also reported.