Some aspects of multiple‐wavelength interaction on solid targets have been experimentally studied at CO2‐laser wavelengths with 1‐nsec pulses. Contrary to predictions, the use of a two‐line (10.6‐ and 9.6‐&mgr;m) source does not reduce the back reflection. This result could be explained by a very short Brillouin interaction length or/and a very low saturation level. The hot‐electron production is also not significantly modified by multiline illumination. A signal at the frequency sum indicates that, even atI&lgr;2as low as 5×1013W cm−2 &mgr;m2, the critical surface is not well defined and that both the 9.6‐ and 10.6‐&mgr;m light interact in the same resonant zone. Finally, significant sidebands were measured at 8.7 and 12 &mgr;m. Some 1 (1)/(2) ‐dimensional simulations with mobile ions indicate that those sidebands probably originate from the beat frequency resonant density at 0.0123nc.