Abstract: A sample containing one or more compounds of high molecular weight is analyzed by irradiating, with a pulsed laser in vacuum, a substrate coated with a thin frozen film of a solution containing the sample. The laser energy is absorbed at the surface of the substrate, rapidly heating the frozen film and ablating the solvent into a vapor plume which carries into the vapor phase entrained molecules of the sample. The vaporized molecules are ionized and accelerated into a mass spectrometer. Mass spectrometric determination of the masses of the ionized molecules of the sample allows the molecular components of the sample to be identified.