Fractures through the waist of the scaphoid were produced experimentally by application of static loads to fresh cadaver specimens. Fractures occurred only when the wrist was in 95° to 100° of dorsiflexion and when the radial portion of the palm received the major part of the load. Definition of these loading conditions allowed us to perform a mathematical analysis of the forces about the scaphoid. The analysis showed that the palmar capsular structures supporting the scaphoid waist were lax when fractures occurred and that the articular surface between the radius and scaphoid bore compressive loads four times greater than the load applied to the palm. This placed the proximal pole of the scaphoid in a vise between the radius and capitate. Fractures predictably occurred at the edge of the vise where the waist of the scaphoid was unsupported. Fractures of the waist of the scaphoid occur as a result of bending loads applied over the distal pole of the scaphoid which is unsupported by the palmar capsule. If these fractures occur while the radial palmar capsule is lax, then tension in this structure should cause malposition of the bony fragments. From this study it appears that the best anatomic reduction of most scaphoid fractures will be obtained when the wrist is placed in such a position that there is laxity in the radial-palmar capsular ligaments, i.e., the wrist in slight palmar flexion and slight radial deviation.