The aim of this work was to study the biodisintegration degree of different pieces made of a biodegradable thermoplastic material, the polylactic acid (PLA) with and without corn in its composition, is studied. The pieces of different shapes and thicknesses were obtained by both injection and extrusion processes, where also a specific foaming additive of polystyrene was added. The PLA and PLA-corn manufactured pieces were subjected to aerobic degradation at a constant temperature of 58+/-2 degrees C for 90 days, following EN 14806 and ISO 20200:2004 Norms. It was found that the pieces made of PLA and PLA with foaming agent had an average biodisintegration degree of 63.6%. With regard to the pieces made of PLA-corn, an average biodisintegration degree of 79.7% was obtained. In this case, the percentage of non degraded material was independent of the size, shape and thickness of the original pieces.