We present molecular line observations, made with angular resolutions of similar to 20 '', toward the filamentary infrared dark cloud G34.43+0.24 using the APEX [CO(3 -> 2), (CO)-C-13(3 -> 2), (CO)-O-18(3 -> 2), and CS(7 -> 6) transitions], Nobeyama 45 m [CS(2 -> 1), SiO(2 -> 1), (CS)-S-34(2 -> 1), HCO+(1 -> 0), (HCO+)-C-13(1 -> 0), and CH3OH(2 -> 1) transitions], and SEST [CS(2 -> 1) and (CO)-O-18(2 -> 1) transitions] telescopes. We find that the spatial distribution of the molecular emission is similar to that of the dust continuum emission observed with 11 '' resolution showing a filamentary structure and four cores. The cores have local thermodynamic equilibrium masses ranging from 3.3 x 10(2) to 1.5 x 10(3) M-circle dot and virial masses from 1.1 x 10(3) to 1.5 x 10(3) M-circle dot, molecular hydrogen densities between 1.8 x 10(4) and 3.9 x 10(5) cm(-3), and column densities > 2.0 x 10(22) cm(-2), values characteristic of massive star-forming cores. The (CO)-C-13(3 -> 2) profile observed toward the most massive core reveals a blue profile indicating that the core is undergoing large-scale inward motion with an average infall velocity of 1.3 km s(-1) and a mass infall rate of 1.8 x 10(-3) M-circle dot yr(-1). We report the discovery of a molecular outflow toward the northernmost core thought to be in a very early stage of evolution. We also detect the presence of high-velocity gas toward each of the other three cores, giving support to the hypothesis that the excess 4.5 mu m emission ("green fuzzies") detected toward these cores is due to shocked gas. The molecular outflows are massive and energetic, with masses ranging from 25 to 80 M-circle dot, momentum 2.3-6.9 x 10(2) M-circle dot km s(-1), and kinetic energies 1.1-3.6 x 10(3) M-circle dot km(2) s(-2), indicating that they are driven by luminous, high-mass young stellar objects.