B767 Captain reports failure of the right main gear to retract after takeoff. After some discussion the flight returns to departure airport for an uneventful landing.

Narrative

Shortly after gear retraction we got a gear disagree message and the right-hand landing gear light indicated down and locked. There was also a light vibration coming from the landing gear area. We asked [ATC] for vectors and eventually holding; which was assigned at 7;000 FT. While the First Officer and I worked the problem using the QRH; the Relief Pilot/Check Airman communicated with Dispatch. Then I spoke to Maintenance Control and asked about lowering the landing gear. After some prodding he confirmed our problem was with the gear up portion of the system; not the gear down part. Following some discussion in the cockpit; we lowered the gear and got three green. We now declared an emergency and advised ATC that we would require the 'equipment upon our landing'. I extended the speedbrakes to expedite fuel burn. We left holding weighing 280;000 pounds and landed uneventfully. [We had a] mechanical failure of the right-hand gear retraction mechanism. I found the gear disagree checklist somewhat confusing. It goes from step 1 to step 4 seemingly bypassing the gear down part.