In this paper, the design process of the acoustics of three churches built in Peru during the last decade is presented. The acoustic design of the first church was done after it was built, while for the last two, the acoustics was considered in the early stage of the general design process. In this work, it is shown how the problems of unfavorable geometries were solved. During the design process, the room parameters were calculated using a computer model, time domain results were always taken into account; at the end, auralization was used as a complement to make final decisions. Since two of the projects were catholic churches, the right reverberation time guarantee the balance between the quality of sacred music and word intelligibility. When possible, measurements were performed once the basic structures of the churches were finished in order to verify the initial model, for the last two cases further measurements were performed when the churches were completely finished. In each church, the sound reinforcement system was also taken into account as part of design process.