[en] The aim of this study was to evaluate the influence of dioxins in the emission levels to the atmosphere by using some waste materials, such as used tires or meat meal, as secondary fuel during the production of clinker. For this purpose, three different cement plants operating in Spain were chosen to perform the project in different sampling episodes. Moreover, different materials were separately evaluated in each plant. Thus, the first plant included the addition in the kiln of meat meal. In the second plant, rejected tires were checked and finally, in the third plant a mixture of both, tires and meat meal, were burned. In all cases, the emission values of dioxins, kept below the limits established by European Union Directives of 0,1 ng I-TEQ/Nm³ with values ranging between 0,001 and 0,042 ng I-TEQ/Nm³. Furthermore, no remarkable differences were found in comparison with reported data obtained in Spanish cement kiln plants when using conventional fuel