Laser-ablated Mo and W atoms react with NO to give primarily the nitride-oxide insertion products NMoO and NWO, but weak MoN and WN absorptions are also observed. The NMoO and NWO molecules are identified from isotopic substitution (Mo-n, N-15, O-18) and density functional theory (DFT) calculations. The M-N and M-O stretching frequencies of the (2)A＇ State NMoO and NWO molecules are predicted by DFT (scale factors 0.936 +/-0.004 and 0.966 +/- 0.005, respectively), but more importantly, the isotopic shifts (and normal modes) are well-described by DFT isotopic frequencies. The higher energy MoNO isomer is observed, but WNO and the M-eta(2)-NO complexes are not found. The M-(eta(1)-NO)(x) (x = 2, 3, 4) complexes are observed: mixed isotopic splittings indicate that Mo(NO)(4) is tetrahedral, like Cr(NO)(4), but the spectra show that W(NO)(4) is distorted to C-2 upsilon symmetry. In addition, a weak 3643.5 cm(-1) combination band and strong 1589.3 cm(-1) fundamental for (NO)(2)(+) and the strong fundamentals for cis-and trans-(NO)(2)(-) were observed.