The simple molecules, water, carbon dioxide, carbon monoxide, and hydrocyanic acid, as well as volatile organic substances have been used to investigate fundamental processes arising during laser tissue interaction. The compounds have been determined by gas chromatography (GC), by gas chromatography in combination with mass spectrometry (GC/MS), and by help of an ion selective electrode. Especially, the dependence of the emitted substances, irradiating porcine tissue (bone, muscle, and liver) with XeCl, TEA CO2, and cw CO2 laser radiation, on different reaction gases are appropriate to obtain information on basic processes. The results demonstrate that oxidation is a process effective in rivalry to the formation of such toxic substances as carbon monoxide, hydrocyanic acid, and styrene as a typical volatile organic compound. The moisture content of tissue is another parameter influencing the interaction processes characteristically. It is possible to reduce the emitted amount of harmful chemicals working in an oxygen containing atmosphere or with a high water content in the reaction zone.