The use of femtosecond-laser sources for the diagnostics of combustion and reacting-flow environments requires detailed knowledge of optical dispersive properties of the medium interacting with the laser beams. Here the second- and third-order dispersion values for nitrogen, oxygen, air, carbon dioxide, ethylene, acetylene, and propane within the 700-900 nm range are reported, along with the pressure dependence of the chromatic dispersion. The effect of dispersion on axial resolution when applied to nonlinear spectroscopy with ultrabroadband pulses is also discussed.