The decomposition of the amino acids alanine and glycine as model Compounds for proteins was studied in sub- and supercritical water. Experiments were carried out in a continuous high pressure plant with a feed solution of 1.0 and 2.0% (g g(-1)) amino acid at 250-450 degrees C, 34 and 24 MPa and residence times of 2.5-35 s. The effect of temperature, residence time, pressure and reactant concentration on conversion and yields of reaction products was elucidated. Based on experimental results reaction networks with the main reactions amino acid decarboxylation and amino acid deamination were formulated for both reactants. Amino acid decomposition kinetics could be described satisfyingly by simple global rate laws. Activation energies are for the alanine decomposition 160 kJ mol(-1) and for the glycine decomposition 156 kJ mol(-1) (C) 2007 Elsevier B.V. All rights reserved.