Summary. During cadaver dissections of 34 adult human hands (fixed in formaldehyd solution), we examined a fibrous complex at the distal end of the flexor retinaculum. This fibrous complex was first mentioned by Legueu and Juvara (1892). It is located always ulno-dorsally to the attachment of the palmaris longus tendon into the palmar aponeurosis. Measurements of this special connective tissue show a mean length of 18.6 mm, a mean height of 4.3 mm and a mean width of 3.1 mm.Also, we looked for the fibrous complex in six adult plastinated transverse sections and in 12 fetal hands where it occurred in a constant way. We also found a very close topographic relationship between these oblique criss-crossed fibers and the palmar cutaneous branch of the median nerve. This nerve regularly gives some ulnar branches to the fibrous complex. The clinical relevance of the fibrous complex is discussed in relationship to a carpal tunnel syndrome. The described transverse fibers of the connective tissue complex are in danger as well as the ulnar branches of the palmar cutaneous nerve when releasing the flexor retinaculum during operation.