For 10 years, in the Surgery Dept. of the University of Pisa, perineal colostomies have been performed on patients who had undergone abdominoperineal rectal amputation. The gracilis muscles of the thighs, transposed to the perineum, are used for building a continent muscular apparatus. Seventeen of 40 patients operated with this procedure have been submitted to defecographic studies, by means of digital fluoroscopic image acquisition. This modality allowed the visualization of anastomotic colon morphology as well as of the functionality of the transposed gracilis muscles during the various phases of defecography. The muscle surrounding the colostomy acts as a sphincter and relaxes only during evacuation; the one positioned as a sling acts as the normal puborectalis muscle. In two patients a perineocele was documented, causing problems in the evacuation phase, which were solved after surgical intervention.