The collisionless infrared multiphoton excitation of small molecules, OCS, SO2, NO2 and DN3 is discussed. Depite the small absorbance of IR photons by these molecules, evidence for the population of highly excited vibronic levels below the dissociation threshold is obtained. Multiphoton dissociation is observed, as well. The average number of photons absorbed and dissociation yields depend predominately on the laser intensity. High order multiphoton processes couple the ground vibrational level with the quasicontinuum of excited levels below and above the dissociation threshold.