One hundred sixty-five cadaveric wrists were dissected to assess the incidence of a medial (hamate) facet on the lunate and any associated pathologic conditions. Forty-seven of these specimens and 137 clinical patients' radiographs were reviewed to attempt to recognize and further assess the incidence of a medial (hamate) facet on the lunate. Two types of lunate were identified. Type I, in which there was no medial facet, was evident in 34.5% of the dissected specimens and type H, in which there was a medial facet, was evident in 65.5% of the dissected specimens. The medial facets in the type II lunates ranged from a shallow 1 mm facet to a deep 6 mm facet. Significant cartilage erosion with exposed subchondral bone at the proximal pole of the hamate, which was not identifiable by radiograph, was evident at dissection in 44.4%) of the type II lunates, while none (0%) of the type I lunates had such associated hamate pathologic conditions. This type II lunate, with the high incidence of associated hamate pathology, may be an unidentified cause of wrist pain on the ulnar side.