The decomposition of plant debris or added organic materials (AOM) in soil have been studied a lot; these represent the input component of soil organic matter (SOM) models. The aim of the experiment was: (i) to compare different kinetic models, (ii) to relate the decomposition parameters of AOM with their biochemical contents. The carbon mineralization kinetics of 17 organic materials of varying composition (from plant and animal origins) were studied in a sandy soil low in organic matter. AOM were incubated with the soil under aerobic conditions at 28°C during six months. Respired-CO2 was measured in triplicates on 17 sampling occasions. AOM were analyzed for carbon, nitrogen, ashes, and fractionated by sequential analyses of fibers, into soluble-, hemicellulose-, cellulose-, and lignin-like fractions characterized for their mass, carbon and nitrogen contents. The mineralized AOM fraction (MAOMF) varied according to the AOM origin: from 12-33% of added C for composts, to 65-90% for those of animal-origin AOM, with many intermediate patterns for those of plant-origin. Seven decomposition models from the literature were fitted to actual MAOMF. Additionally, a simplified version of a parallel three-compartment model (m6) was proposed. A compromise between the precision of the predictions and the simplicity of the formulae allowed the recommendation of m6 defined by: (i) very labile L', resistant R' and stable S compartments with fixed kinetic constants, (ii) two parameters PL' and PS (proportions of L' and S, P'R=1-PL'-Ps). We tested for the best prediction of the above parameters with direct or combined (e.g. lignin/nitrogen) analytical data. For the whole AOM set, the resulting equations explained 96.3, and 96.0% of PL' and PS, respectively. These predictions were significant, but to a lesser degree for CO2-mineralization of AOM with contrasting characteristics. A principal component analysis was used to classify AOM according to their biochemical contents into two