A precise anatomical study of the fascias within the retrorectal space is reported, analyzing and clarifying the anatomical concepts previously employed to describe Waldeyer's and the rectosacral fascia. The pelvis was dissected in 15 cadavers (10 males and five females). All specimens were divided in the median sagittal plane including the middle axis of the anal canal, to allow a correct visualization of and access to the retrorectal space. The retrorectal space was limited anteriorly by the rectum and posterior mesorectum covered by a fine visceral fascia, and posteriorly by the sacrum covered by the parietal presacral fascia. The rectosacral fascia divided the retrorectal space into inferior and superior portions in 80% of the male and 100% of the female specimens. It originated from the presacral parietal fascia at the level of S2 in 15%, S3 in 38% and S4 in 46% of specimens. In all cases it passed caudally to join the rectal visceral fascia 3-5 cm above the anorectal junction. As described by Waldeyer, the floor of the retrorectal space is formed by the fusion of the presacral parietal fascia and the rectal visceral fascia and lies above the levator ani muscle at the level of the anorectal junction. The rectosacral fascia divides the retrorectal space into inferior and superior portions. This must be differentiated from Waldeyer's description of the fascia lying in the inferior limit of the retrorectal space, formed by the fusion of the rectal visceral and parietal fascias.