The interactions of lasers with matter are manyfold. Among the important interactions is the generation of pressure waves by laser heating in an optically absorbing dye. The conversion of energy from transient laser heating to an acoustic wave is considered in detail in this paper. As a laser pulse enters an absorbing dye, energy is absorbed and converted into heat. Part of it will appear as elastic energy in the form of a pressure wave, due to very small expansion in the dye during the laser pulse.