The strength of tissue against individual sutures in structures used in the repair of inguinal hernia was tested in situ in 19 cadavers. Altogether 465 measurements were made. Three different layers were investigated, and the mean tissue strength to a single suture was recorded as the mean of all means for each preparation and aspect as follows. (1) The superficial layer (external oblique aponeurosis). Superior aspect 5.3 kp, inferior aspect 5.5 kp. (2) Middle layer. Superior aspect (internal abdominal oblique), 5.9 kp; inferior aspect (inferior border of the inguinal ligament), 6.8 kp. (3) Deep layer. Superior aspect (transversalis fascia), 5.3 kp; inferior aspect (ilio-pubic tract), 6.9 kp. In Cooper's ligament the mean holding power of the tissue against a single suture was found to be 9.1 kp. The site of the most medial of the sutures in the superior aspect of the middle layer corresponds to the conjoined tendon, and the mean tissue strength to this suture was 11.0 kp. The findings thus suggest that the strengths of the tissues of the anterior and posterior walls of the inguinal canal are roughly equal. The structures making up the conjoined tendon and Cooper's ligament were strongest, however, and showed tissue strengths nearly twice those of other structures.