In the present paper the results of some tests performed on concrete specimens reinforced with fibers made from waste polyethylene terephthalate (PET) bottles are reported. The fibers have been obtained by simply cutting the bottles; the fibers are then added to the mix concrete or they are used as discrete reinforcement of specimens and little beams in substitution of steel bars. The tests are to be considered as an approach to a more extensive investigation on the use of PET as a reinforcing material for concrete and masonry structures. The results that have been obtained are very interesting, especially regarding the adherence between PET and concrete, suggesting a possible use of this material in the form of flat or round bars, or networks for structural reinforcement.