Isolated posttraumatic subluxation of the extensor carpi ulnaris tendon at the wrist has received scant attention in the literature. Five patients with this condition were seen during a 21-month period. All had chronic subluxation resulting from forearm hypersupination injury sustained during an athletic activity. Surgical treatment was indicated for three patients, and each obtained a satisfactory result. The salient pathologic feature appears to be a disruption of the ulnar-restraining septum of the sixth dorsal compartment of the wrist. Surgical treatment by reconstruction of this structure appears to be reliable and beneficial.